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Test H: Fuel Control: Testing

NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION  table of fault code setting condition.
NOTE: Test procedure begins with step 20). No test procedures have been omitted.
FAULT CODE SETTING CONDITION

Fault Code KOEO KOER Continuous Memory
P0131      H27
P0132  H115  H115  H115
P0133      H20
P0135 1   H30  H30  H30
P0136      H80
P0138  H115  H115  H115
P0141 1   H25  H25  H25
P0151      H27
P0152  H115  H115  H115
P0153      H20
P0155 1   H30  H30  H30
P0156      H80
P0158  H115  H115  H115
P0161 1   H25  H25  H25
P0171 1       H41
P0172 1       H41
P0174 1       H41
P0175 1       H41
P0201  H56  H56  H56
P0202  H56  H56  H56
P0203  H56  H56  H56
P0204  H56  H56  H56
P0205  H56  H56  H56
P0206  H56  H56  H56
P0207  H56  H56  H56
P0208  H56  H56  H56
P0209  H56  H56  H56
P0210  H56  H56  H56
P0211  H56  H56  H56
P0212  H56  H56  H56
P1127 1     H100  
P1128 1     H110  
P1129 1     H110  
P1130 1       H40
P1131 1       H40
P1132 1       H40
P1137    H80  
P1138    H80  
P1150 1       H40
P1151 1   H40  H40  H40
P1152 1     H40  H40
P1157    H80  
P1158    H80  
(1)
For Natural Gas Engines see FAULT CODE SETTING CONDITION .
    NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  1. 20) Continuous Memory DTCs P0133 Or P0153: Perform KOER Self-Test
    Perform KOER ON-DEMAND SELF-TEST under QUICK TEST. If either DTC P1127, P1128 or P1129 is present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If DTC P1127, P1128 or P1129 are not present, go to next step.

  2. 21) DTC P0133 & P0153: HO2S Response Test

    DTC P0133 or P0153 are set during self-test when frequency and amplitude fall below a calibrated limit in HO2S as follows:

    Possible causes are:

    • HO2S Sensor Contaminated
    • Exhaust Leaks
    • Open Or Shorted Circuit
    • Improper Fueling
    • Faulty MAF Sensor
    • Deteriorating HO2S Sensor
    • Leak In Air Induction System

    Turn ignition switch to ON position. Using scan tool, access GENERIC OBD-II FUNCTIONS. Press CONTINUE. Select DIAGNOSTIC MONITORING TEST RESULTS from menu and press enter. Scroll to TEST ID: 01 and press enter. Press START. Turn ignition switch to OFF position.

    NOTE: For additional information on HO2S testing with scan tool, see TESTING under HEATED OXYGEN SENSOR MONITOR under DIAGNOSTIC MONITORING TESTS.

    If measured value is less than minimum threshold, go to step  23). If measured value is more than minimum threshold, fault cannot be identified at this time. Perform PCM RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Perform DRIVE CYCLE PROCEDURE under DIAGNOSTIC MONITORS. Ensure HO2S MONITOR PROCEDURE is performed. Repeat step  20). If no DTCs are present, testing is complete.

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 23). No test procedures have been omitted.

  3. 23) Check For Unmetered Air Leaks

    Fuel calculations can be affected by unmetered air (vacuum) leaks. Check the following as potential source of air leak:
    • Hoses Connected To MAF Sensor Or Throttle Body Leaking
    • Intake Manifold Gasket Leaking
    • PCV System Disconnected
    • Vacuum Lines Disconnected
    • Poorly Seated Oil Dip Stick &/Or Dipstick Tube Or Cap
    • Exhaust Leaks At Flanges Or Gaskets

    If none of these conditions are present, go to next step. If any of these conditions are present, repair source of air leak as necessary. Perform PCM RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Perform DRIVE CYCLE PROCEDURE under DIAGNOSTIC MONITORS. Ensure HO2S MONITOR PROCEDURE is performed.

    4. NOTE: HO2S may be displayed as O2S on scan tool.

  4. 24) Check HO2S Circuit Wiring
    Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector. Check for water contamination. Clean and repair as necessary. Connect a jumper wire between HO2S SIG and VPWR circuits at suspect HO2S harness connector. See Figure or Figure . Turn ignition switch to ON position. Using scan tool, access appropriate HO2S PID (11, 12, 21 or 22) from PID/DATA MONITOR & RECORD menu. If HO2S PID voltage is 1.5 volts or less, turn ignition switch to OFF position, remove jumper wire and go to next step. If HO2S PID voltage is more than 1.5 volts, replace faulty HO2S. Change engine oil and filter. Perform PCM RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Perform DRIVE CYCLE PROCEDURE under DIAGNOSTIC MONITORS. Ensure HO2S MONITOR PROCEDURE is performed.
    5. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  5. 25) KOEO, KOER & Continuous Memory DTCs P0141 & P0161: Check HO2S Heater, SIG Or SIG RTN Circuits For Open
    DTC P0141 or P0161 are set during self-test when current draw exceeds a calibrated limit or an open or short is detected in HO2S heater as follows:

    Turn ignition switch to OFF position. Disconnect suspect HO2S connector and PCM connector(s). Inspect connectors for loose, damaged or corroded terminals. Check HO2S circuit for exposed wiring, water contamination, corrosion and proper assembly. Repair as necessary. Using a DVOM, measure resistance of suspect HO2S SIG and SIG RTN circuits between PCM harness connector and HO2S harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Figure or Figure . If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open in HO2S SIG or SIG RTN circuit. Perform DRIVE CYCLE PROCEDURE under DIAGNOSTIC MONITORS. Ensure HO2S MONITOR PROCEDURE is performed.

    PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION

    Application PCM Terminal No.
    Cougar
    HO2S-11 SIG 60
    HO2S-11 HTR (1) 73
    HO2S-12 SIG 35
    HO2S-12 HTR 100
    HO2S-21 SIG 87
    HO2S-21 HTR 99
    HO2S-22 SIG 61
    HO2S-22 HTR 101
    PWR GND 51, 77 & 103
    SIG RTN 91
    VPWR 71 & 97
    VREF 90
    LS & Thunderbird
    HO2S-11 SIG C45
    HO2S-11 HTR C7
    HO2S-12 SIG B28
    HO2S-12 HTR B15
    HO2S-21 SIG C44
    HO2S-21 HTR C8
    HO2S-22 SIG B29
    HO2S-22 HTR B16
    PWR GND A24-A27 & A43
    SIG RTN A17, B17 & C17
    VPWR A32 & A33
    VREF A20 & C20
    Explorer & Mountaineer
    HO2S-11 SIG C17
    HO2S-11 HTR C7
    HO2S-12 SIG B17
    HO2S-12 HTR B15
    HO2S-21 SIG C17
    HO2S-21 HTR C8
    HO2S-22 SIG B17
    HO2S-22 HTR B16
    PWR GND A24-A27
    SIG RTN A17, B17 & C17
    VPWR A32 & A33
    VREF A20 & C20
    All Others
    HO2S-11 SIG 60
    HO2S-11 HTR 93
    HO2S-12 SIG 35
    HO2S-12 HTR 95
    HO2S-21 SIG 87
    HO2S-21 HTR 94
    HO2S-22 SIG 61
    HO2S-22 HTR 96
    PWR GND 51, 77 & 103
    SIG RTN 91
    VPWR 71 & 97
    VREF 90
    (1) Cougar 2.0L is terminal No. 93.

  6. 26) Check HO2S SIG Circuit For Short To VPWR

    Disconnect scan tool from Data Link Connector (DLC). Using a DVOM, measure resistance between HO2S and VPWR circuits at PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If resistance measurement is more than 10 k/ohms, go to next step. If resistance measurement is 10 k/ohms or less, go to step  28).
    Fig 1: Identifying Powertrain Control Module Connector Terminals (150-Pin)
    G00011081Courtesy of FORD MOTOR CO.
    Fig 2: Identifying Powertrain Control Module Connector Terminals (104-Pin)
    G96F31315Courtesy of FORD MOTOR CO.
    7. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  7. 27) Check For Source Of Potential HO2S Contamination
    Check the following areas for cause of contamination:
    • Use Of Unapproved Silicone Sealers
    • Fuel Contaminated By Silicone Additives
    • Excessive Oil Burning (Such As; Rings, Valve Seals And Oil Overfill)
    • Antifreeze (Glycol) Leaking Internally In Engine
    • Lead Contaminated Fuel
    • Short Trip Driving In Cold Weather
    • Use Of Unapproved Cleaning Products

    If contamination exists, repair source of contamination and replace faulty HO2S, oil and filter. Perform PCM RESET PROCEDURE under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Perform DRIVE CYCLE PROCEDURE under DIAGNOSTIC MONITORS. Ensure HO2S MONITOR PROCEDURE is performed. If contamination does not exist and you were directed here to diagnose DTC P0141 or P0161, go to step  30), for all others replace PCM.

  8. 28) Verify Wiring Is In Proper Terminal Location

    Ensure suspect HO2S harness connector and PCM is disconnected. Using a DVOM, measure resistance of HO2S SIG and SIG RTN circuits between PCM harness connector and HO2S harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Figure or Figure . If both resistance measurements are less than 5 ohms, replace HO2S. If either resistance measurement is 5 ohms or more, repair wiring as necessary.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 28) to step 30). No test procedures have been omitted.
    9. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  9. 30) DTC P0135 Or P0155: HO2S Heater Circuit Shorted To GND Or VPWR, Or Excessive Or Low Current Draw
    These DTCs indicate a short to VPWR, or an open VPWR or GND circuit in HO2S heater circuit causing current draw to exceed calibrated limit. HO2S DTC identification is as follows:
    • DTC P0135 Is For HO2S-11
    • DTC P0141 Is For HO2S-12
    • DTC P0155 Is For HO2S-21
    • DTC P0161 Is For HO2S-22

    Refer to illustrations for HO2S identification. See Figure-Figure . Possible causes are:

    • Short To VPWR Or HO2S Circuit In Harness
    • Water In Connectors
    • Open In GND Or VPWR Circuit
    • Low Battery Voltage
    • Corroded Or Poorly Connected Terminals
    • Damaged HO2S Heater
    • Damaged Powertrain Control Module (PCM)
    • Faulty HO2S Heater

    Inspect HO2S circuit for exposed wiring, water contamination, corrosion and proper assembly. Repair as necessary. If HO2S connectors are okay, go to next step.

  10. 31) Perform KOEO On-Demand Self-Test

    Start engine and operate at 2000 RPM for one minute. Turn ignition switch to OFF position. Perform KOEO ON-DEMAND SELF-TEST . If either DTC P0135, P0141, P0155 or P0161 is present, go to next step. If specified DTCs are not present, go to step  33).
    11. NOTE: If pairs of DTCs P0135 and P0155, or P0141 and P0161 are retrieved, both HO2S HTR circuits will require testing. DTCs retrieved individually, are to be tested individually.

  11. 32) Check VPWR Voltage To HO2S Harness Connector
    Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector(s). Inspect wiring harness for damage and repair as necessary. Turn ignition switch to ON position. Using a DVOM, measure voltage between SIG RTN and VPWR circuits at suspect HO2S harness connector. See Figure or Figure . If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, go to TEST B, step 5) (150-pin PCM models), or check VPWR circuit fuse to HO2S heater (all others). If VPWR fuse is blown, check VPWR circuit for short to ground. See WIRING DIAGRAMS article. Replace fuse and repair circuit as necessary. If VPWR circuit fuse is okay, repair open in VPWR circuit. See WIRING DIAGRAMS article.

  12. 33) Check HO2S HTR Circuit For Short To PWR GND, SIG RTN Or VPWR

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between suspect HO2S HTR circuit, and PWR GND, SIG RTN and VPWR circuits at suspect HO2S harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION . See Figure or Figure . If all resistance measurements are more than 10 k/ohms, go to next step. If any resistance measurement is 10 k/ohms or less, repair short in affected circuit.

  13. 34) Check HO2S HTR Circuit For Open In Harness

    Leave ignition switch in OFF position and HO2S disconnected. Using a DVOM, measure resistance of suspect HO2S HTR circuit between PCM harness connector and HO2S harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Figure or Figure . If resistance is 5 ohms or more, repair open circuit or excessive resistance in HO2S HTR circuit. If resistance is less than 5 ohms, go to next step.

  14. 35) Check HO2S HTR Resistance

    Using a DVOM, measure resistance between HO2S HTR and VPWR circuits at suspect HO2S connector. See Figure or Figure . If resistance is 3-30 ohms, go to next step. If resistance is not 3-30 ohms, replace HO2S.

  15. 36) Check HO2S Case For Short To VPWR, HTR Or SIG RTN

    Using a DVOM, measure resistance between HO2S component case and HO2S HTR, SIG RTN and VPWR circuits at HO2S connector. If all resistance measurements are more than 10 k/ohms, replace PCM. If any resistance measurement is 10 k/ohms or less, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 36) to step 40). No test procedures have been omitted.
    16. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  16. 40) DTCs P1130, P1131, P1132, P1150, P1151 & P1152: Upstream HO2S Or Fuel System Not Switching
    DTCs P1131 and P1151 indicate air/fuel ratio is correcting rich for an overly lean condition. DTCs P1132 and P1152 indicate air/fuel ratio is correcting lean for an overly rich condition. DTCs P1130 and P1150 indicate when an HO2S fails to switch due to a circuit or fuel exceeding a calibrated limit. HO2S DTC identification is as follows:
    • DTCs P1130, P1131 & P1132 are for HO2S-11.
    • DTCs P1150, P1151 & P1152 are for HO2S-12.

    Possible causes are:

    • Fuel System

      Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or engine running out of fuel or vapory recovery system fault.

    • Induction System

      Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or improperly seated engine oil dipstick.

    • EGR System

      Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.

    • Engine Mechanical

      Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.

    Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to TEST DC, step 25) .

    17. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  17. 41) Continuous Memory DTC P0171, P0172, P0174 Or P0175: Fuel System At Corrected Fuel Trim
    All Continuous Memory ignition and misfire DTCs must be serviced prior to servicing any fuel trim DTCs. DTCs P0171, P0172, P0174 and P0175 indicate a concern when adaptive fuel strategy senses a lean or rich condition beyond minimum or maximum calibrated limit. Fuel system DTC identification is as follows:

    • Bank No. 1

      DTCs P0171 (lean), and P0172 (rich).

    • Bank No. 2

      DTCs P0174 (lean), and P0175 (rich).

    Possible causes for these faults are:

    • Fuel System

      Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or engine running out of fuel or vapory recovery system fault.

    • Induction System

      Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or improperly seated engine oil dipstick.

    • EGR System

      Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.

    • Engine Mechanical

      Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.

    Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to TEST DC, step 25) .

  18. 42) Perform KOER Self-Test

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold. Start engine, and operate at 2000 RPM for 5 minutes, then allow to return to idle. Perform KOER ON-DEMAND SELF-TEST and proceed as follows:
    • If KOER DTCs P1127, P1128 or P1129 are present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
    • If KOER DTC (P1130, P1131) or (P1150, P1151) is present, go to next step.
    • If KOER DTC (P1130, P1132) or (P1150, P1152) is present, go to step  49).

    If none of these DTCs are present, proceed as follows:

    • If Continuous Memory DTC P1130, P1150, P0171, P0172, P0174 or P0175 is present, go to step  52).
    • If DTCs P1132 and/or P1152 is no longer present, reconnect fuel vapor hose.
    • If directed to this test to diagnose DTCs P1131, P1132, P1151 and/or P1152, perform evaporative system leakage tests. See EVAPORATIVE EMISSIONS DIAGNOSTIC TROUBLE CODE DEFINITIONS .
    • If no DTCs have repeated and no DTCs are present, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .

  19. 43) HO2S Circuit Test (With Lean DTCs)

    Disconnect HO2S harness connector that is related to DTC retrieved. Turn ignition switch to ON position. Using scan tool, access appropriate HO2S PID (11, 12, 21 or 22) from PID/DATA MONITOR & RECORD menu. Connect a jumper wire between HO2S SIG and VPWR circuits at suspect HO2S harness connector.
    NOTE: If spark occurs when connecting jumper wire (indicating a short circuit), remove jumper wire, check fuse in HO2S HTR circuit and go to step  47).

    If HO2S PID voltage is 1.3 volt or more, check SIG RTN circuit for open. Go to next step. If voltage is less than 1.3 volt, go to step  46).

  20. 44) Check SIG RTN Circuit For Open

    Turn ignition switch to OFF position. Using a DVOM, measure resistance of SIG RTN circuit between negative battery terminal and suspect HO2S harness connector. See Figure or Figure . If resistance is less than 5 ohms, go to step  52). If resistance is 5 ohms or more, go to next step.

  21. 45) Check HO2S SIG RTN Circuit For Open In Harness

    Ensure ignition switch is in OFF position and PCM connector(s) is disconnected. Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector and suspect HO2S harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2, Fig 1, Figure and Figure . If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open in SIG RTN circuit.

  22. 46) Check HO2S SIG Circuit For Open

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. Ensure suspect HO2S harness connector is disconnected. Using a DVOM, measure resistance of HO2S SIG circuit between suspect HO2S harness connector and appropriate PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2, Fig 1, Figure and Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in SIG RTN circuit.

  23. 47) Check HO2S SIG Circuit For Short To Ground

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Ensure suspect HO2S harness connector is disconnected. Using a DVOM, measure resistance between HO2S SIG, and PWR GND and HO2S SIG RTN circuits at PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If both resistance measurements are more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, repair short between affected circuits.

  24. 48) Check HO2S For Short To Ground

    Leave PCM disconnected. Reconnect suspect HO2S connector. Using a DVOM, measure resistance between HO2S SIG, and PWR GND and HO2S SIG RTN circuits at PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If both resistance measurements are 10 k/ohms or less, replace faulty HO2S. If both resistance measurements are more than 10 k/ohms, replace PCM.

  25. 49) Check HO2S Circuit (Rich DTCs)

    Ensure ignition switch is in OFF position. Disconnect HO2S harness connector that is related to DTC retrieved. Turn ignition switch to ON position. Using scan tool, access appropriate HO2S PID (11, 12, 21 or 22) from PID/DATA MONITOR & RECORD menu. If HO2S PID voltage is more than .2 volt, go to next step. If HO2S PID voltage is .2 volt or less, go to step  51).

  26. 50) Check HO2S SIG Circuit For Short To VPWR & HO2S HTR Circuits

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between HO2S SIG, and VPWR and HO2S HTR circuits at PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If both resistance measurements are more than 10 k/ohms, replace PCM. If either resistance measurement is 10 k/ohms or less, repair short between affected circuits.

  27. 51) Check HO2S SIG For Short To HO2S HTR Circuit In Sensor

    Turn ignition switch to OFF position. Ensure suspect HO2S harness connector is disconnected. Using a DVOM, measure resistance between HO2S SIG and HO2S HTR circuits at suspect HO2S connector. See Figure and Figure . If resistance measurement is more than 10 k/ohms, go to next step. If resistance measurement is 10 k/ohms or less, replace internally shorted HO2S.
    28. WARNING: Always refer to safety procedures to reduce possibilty of injury. See FUEL SYSTEM SAFETY PRECAUTIONS .
    NOTE: Fuel pump will only operate for 8 seconds when OUTPUT TEST MODE is activated.
    Fig 3: Fuel System Types, Fuel Injector Resistances & Pressure Specifications
    G00077798Courtesy of FORD MOTOR CO.

  28. 52) Check Fuel Pressure
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE procedure under FUEL SYSTEM in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install fuel pressure gauge. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE under ADDITIONAL SYSTEM FUNCTIONS. Command fuel pump ON and run fuel pump to obtain maximum fuel pressure. Record fuel pressure. Compare measured fuel pressure to fuel pressure specification in illustration. See Fig 3. If fuel system pressure is not as specified, go to TEST HC, step  1). If fuel system pressure is as specified, go to next step.

  29. 53) Check Fuel System For Pressure Stability With Ignition On (Slow Leakdown)

    With fuel pressure gauge installed, cycle ignition from OFF to ON position 3-4 times to pressurize fuel system (DO NOT start engine). Note fuel pressure with ignition switch turned to ON position. If fuel pressure does not remain within 5 psi (34 kPa) of maximum pressure after 10 seconds, check fuel system for external leaks. If an external leak is detected, go to TEST HC, step  1). If an external leak is not detected, go to step  55).

  30. 54) Check Fuel System For Pressure Stability With Ignition ON

    With fuel pressure gauge installed, cycle ignition from OFF to ON position 3-4 times to pressurize fuel system (DO NOT start engine). Note fuel pressure with ignition switch turned to ON position. If fuel pressure remains within 5 psi (34 kPa) of maximum pressure after one minute, go to TEST HC, step  5). If fuel pressure does not remain within 5 psi (34 kPa) of maximum pressure after one minute, go to step  56) (for HO2S DTCs displayed with Misfire DTCs), or go to step  59) (for all other DTCs).
    31. NOTE: For additional information on Misfire DTCs and setting conditions, go to MISFIRE DETECTION MONITORING under DIAGNOSTIC MONITORING TESTS under ADDITIONAL SYSTEM FUNCTIONS.

  31. 55) Check Injector Fault PIDs & Associated DTCs
    Turn ignition switch to ON position. Using scan tool, access INJ1F-INJ10F PIDs from PID/DATA MONITOR & RECORD menu. If misfire DTCs are present (P0301-P0310), only select injector fault PID(s) that correspond to appropriate misfire DTC(s). If DTCs P0201-P0212 or an injector fault(s) is present, go to next step. If no injector fault is present and only Misfire DTCs P0300-P0310 are present, go to TEST HD, step  12). If DTCs P0201-P0212 are not present, no injector fault(s) are present, and any other DTC is present, go to step  59).
    32. NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: Performing this test step will clear Continuous Memory DTCs.

  32. 56) KOEO, KOER & Continuous Memory DTC P0201-P0212: Check Fuel Injector & Circuit Resistance
    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Use injector fault PID noted in step  55) to determine fuel injector circuits that require testing. Using a DVOM, measure and record resistance between suspect fuel injector circuit and VPWR circuits at PCM harness connector. See PCM FUEL INJECTOR, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . Resistance should be 11-18 ohms. If resistance is not as specified, go to next step. If resistance is as specified, concern may be intermittent. Go to TEST Z, step 1) . If unable to duplicate concern, replace PCM.
    PCM FUEL INJECTOR, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION

    Application PCM Terminal No.
    Cougar
    Injector No. 1 70
    Injector No. 2 96
    Injector No. 3 20
    Injector No. 4 95
    Injector No. 5 (1) 93
    Injector No. 6 (1) 94
    PWR GND 24, 51, 77 & 103
    VPWR 71 & 97
    Explorer, LS, Mountaineer & Thunderbird
    Injector No. 1 C2
    Injector No. 2 C14
    Injector No. 3 C24
    Injector No. 4 C32
    Injector No. 5 C11
    Injector No. 6 C21
    Injector No. 7 (1) C29
    Injector No. 8 (1) C37
    PWR GND A24 & A26
    VPWR A32 & A33
    All Others
    Injector No. 1 75
    Injector No. 2 101
    Injector No. 3 74
    Injector No. 4 100
    Injector No. 5 (1) 73
    Injector No. 6 (1) 99
    Injector No. 7 (1) 72
    Injector No. 8 (1) 98
    Injector No. 9 (1) 68
    Injector No. 10 (1) 42
    PWR GND 51, 77 & 103
    VPWR 71 & 97
    (1) If applicable.

  33. 57) Check Fuel Injector Harness Resistance

    Turn ignition switch to OFF position. Disconnect suspect fuel injector harness connector. Using a DVOM, measure resistance of fuel injector circuit signal and VPWR circuit between PCM harness connector and suspect fuel injector harness connector. See PCM FUEL INJECTOR, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2, Fig 1 and Fig 4 . If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open in fuel injector signal or VPWR circuit.
    Fig 4: Identifying Fuel Injector Connector Terminals
    G99D02109Courtesy of FORD MOTOR CO.

  34. 58) Check Fuel Injector Harness Circuit For Short To PWR Or GND

    Turn ignition switch to OFF position. Disconnect PCM harness connector(s). Ensure suspect fuel injector is disconnected. Using a DVOM, measure resistance between SIG circuit, and PWR GND and VPWR circuits at PCM harness connector. See PCM FUEL INJECTOR, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If each resistance measurement is more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, repair short between circuits.

  35. 59) Flow Test Fuel Injector(s)

    Turn ignition switch to OFF position. Reconnect PCM and fuel injector connector(s). Use Rotunda fuel injector tester from Fuel Tester Kit (113-00114) to flow test fuel injectors. Follow injector tester instructions. If fuel injector flow or leakage rate is not okay, replace defective fuel injector(s). If flow rate for each fuel injector is okay, proceed as follows:
    • For DTCs P1131 and P1151, go to next step.
    • For DTCs P0171, P0174, P1130, and P1150, go to step  61).
    • For DTCs P1132 and P1152, go to step  64).
    • For DTCs P0172 and P0175, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .
    36. NOTE: If vehicle is not equipped with secondary air injection, go to next step.

  36. 60) Check For Secondary Air Intrusion
    Possible causes for an HO2S always lean condition are:
    • Leak In Hoses From Secondary Air Injection Pump
    • Secondary Air Diverted Upstream Of HO2S

    Turn ignition switch to OFF position. Disconnect secondary air injection hoses from engine and plug engine side of air injection ports. Start engine and allow to reach operating temperature. Perform KOER ON-DEMAND SELF-TEST . If DTC P1131 or P1151 is present, go to next step. If DTCs P1131 or P1151 are not present, check secondary air injection system. See TEST HM, step  7).

  37. 61) Check Air Induction System For Air Leaks

    Check inlet tubes from air cleaner to throttle body for leaks. Check PCV system for leaks. Check vacuum hoses for damage and tight connections. Check upper and lower intake manifold gaskets. If any faults are found, repair as necessary. If no faults are found, proceed as follows:
    • For Continuous Memory DTCs P0171, P0174, P1130 or P1150, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .
    • For DTCs P1131 and P1130, or P1151 and P1150, go to next step.

  38. 62) Check Cylinder Compression

    Use Misfire DTCs retrieved in step  55) to determine which cylinder compression is suspect. Using compression gauge, check compression on all cylinders. Note suspect cylinder compression. Lowest cylinder compression should be more than 75 percent of highest cylinder compression reading. If suspect cylinder compression is not within specification, repair engine as necessary. If suspect cylinder compression is within specification, go to next step (if directed here for DTCs P1130, P1131, P1150 and P1151), or step  64) (if directed here for DTCs P1132 and P1152). If misfire DTCs are displayed with fuel control DTCs, go to TEST HD, step  20).

  39. 63) Check HO2S Ability To Generate Voltage More Than .5 Volt

    Vacuum or air leaks can cause DTCs P1130, P1131, P1150, and P1151. Possible causes are:
    • Water Contamination In Connector
    • Leaking Vacuum Actuators
    • Engine Sealing Concerns (Intake & IAC Valve)
    • Faulty EGR Valve
    • Faulty PCV System
    • Unmetered Air Leaks Between Throttle Body & MAF Sensor

    Turn ignition switch to OFF position. Inspect HO2S wiring harness for chafing, burned wires or other damage. Repair as necessary. Disconnect suspect HO2S connector. Connect DVOM between HO2S SIG circuit, and SIG RTN or HO2S GND circuits at suspect HO2S connector. Start engine and operate at 2000 RPM for 3 minutes. Perform KOER ON-DEMAND SELF-TEST while monitoring HO2S voltage. If HO2S voltage increases to more than .5 volt, go to step  70). If voltage is .5 volt or less, replace faulty HO2S.

  40. 64) Attempt To Generate DTC P1131 Or P1151

    Disconnect suspect HO2S connector. Connect a jumper wire between negative battery terminal and HO2S SIG circuit at suspect HO2S harness connector. Perform KOER ON-DEMAND SELF-TEST . If DTC P1131 or P1151 is present, turn ignition switch to OFF position, remove jumper wire and go to next step. If DTC P1131 or P1151 is not present, turn ignition switch to OFF position, remove jumper wire and reconnect HO2S harness connector. Disconnect and check PCM harness connector(s) for damaged or pushed out terminals, moisture or corrosion and repair as necessary. If PCM connector(s) is okay, replace PCM.

  41. 65) HO2S Sensor Voltage Check

    Leave HO2S disconnected. Connect DVOM between HO2S SIG and SIG RTN circuits at suspect HO2S connector. Disconnect any vacuum hose from vacuum tree (simulates lean condition). Start engine and operate at 2000 RPM. If DVOM reads less than .4 volt within 30 seconds, turn ignition switch to OFF position, reconnect vacuum hose and HO2S and go to step  70). If DVOM reads .4 volt or more after 30 seconds, replace HO2S and repeat KOER ON-DEMAND SELF-TEST . If DTCs P1132 or P1152 are still present, replace PCM.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 65) to step 70). No test procedures have been omitted.
    42. NOTE: HO2S may be displayed as O2S on scan tool.
    NOTE: DO NOT compare HO2S switch rate from bank No. 1 to bank No. 2 as an indication of sensor's function. It is normal to have a variance in switch ratio from bank to bank.

  42. 70) Monitor HO2S PID For Switching While Performing Wiggle Test
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Ensure engine is at normal operating temperature. Using scan tool, access suspect HO2S PID (11, 12, 21 or 22) from PID/DATA MONITOR & RECORD menu. Monitor suspect HO2S PID while wiggling and bending small sections of wiring harness between suspect HO2S and PCM.

    If suspect HO2S PID voltage stops switching, isolate fault and repair as necessary. If suspect HO2S PID voltage switches, turn ignition switch to OFF position and go to next step.

  43. 71) Monitor HO2S PID Switching During Test Drive

    This test step requires an assistant. Using scan tool, access LOOP PID and ensure vehicle is in closed-loop before proceeding. Test drive vehicle in a manner consistent with Freeze Frame Data in an attempt to duplicate original concern. Using an assistant, observe suspect HO2S PID. If suspect HO2S PID voltage switches, system is okay at this time and testing is complete. If suspect HO2S PID voltage does not switch, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 71) to step 80). No test procedures have been omitted.
    44. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  44. 80) Continuous Memory DTC P0136, P0156: Monitor Downstream HO2S Output Voltage For Activity; KOER DTC P1137, P1138, P1157 & P1158: Indicate Lack Of HO2S Switching
    DTCs P0136 and P0156 indicate output voltage of downstream HO2S did not meet calibrated limits. DTCs P1137, P1138, P1157 or P1158 indicate PCM does not detect output of HO2S in a calibrated amount of time (lean condition). DTCs P0136, P1137 and P1138 are for HO2S-12. DTCs P0156, P1157 and P1158 are for HO2S-22. See Figure-Figure . Possible causes are:
    • Damaged Wiring Harness Or Connector
    • Crossed Sensor Wires
    • Exhaust System Leaks
    • Contaminated Or Faulty HO2S

    Service any Continuous Memory ignition and Misfire DTCs before continuing. If no Continuous Memory ignition or Misfire DTCs are present, check for possible causes listed in this step. Repair as necessary. If no faults are found, go to next step (DTCs P0136 and P0156), or go to step  82) (all other DTCs).

  45. 81) Check For KOER DTCs P1137, P1138, P1157 Or P1158

    Start engine, and operate at 2000 RPM for 3 minutes. Perform KOER ON-DEMAND SELF-TEST . If any combination of DTCs P1137, P1138, P1157 or P1158 is present along with P0136 or P0156, go to next step. If only DTC P0136 or P0156 is present, check for intermittent faults. Go to TEST Z, step 1) .
    46. NOTE: DTCs P0136 and P0156 can be set when leaks exist in exhaust system between engine and rear of catalytic converter.

  46. 82) Check Exhaust System For Leaks
    Inspect exhaust system including catalytic converter and HO2S for the following:
    • Incorrect HO2S Torque
    • Exhaust System Leaks
    • Punctures Or Cracks In Pipes Leading To Or In Catalytic Converter

    Repair as necessary. If exhaust system is okay, go to next step.

  47. 83) Check HO2S SIG Circuit For Short To VPWR, VREF, SIG RTN Or PWR GND Circuits

    Turn ignition switch to OFF position. Ensure suspect HO2S is disconnected. Disconnect scan tool from DLC. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between suspect HO2S SIG circuit, and PWR GND, SIG RTN, VPWR and VREF circuits at PCM harness connector (both VREF circuits on 150-pin PCM). See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If all resistance measurements are more than 10 k/ohms, go to next step. If any resistance measurement is 10 k/ohms or less, repair short between HO2S SIG and PWR GND, SIG RTN, VPWR or VREF circuit.

  48. 84) Check HO2S SIG & SIG RTN Circuits For Open In Harness

    Using a DVOM, measure resistance of HO2S SIG, SIG RTN and VPWR circuits between suspect HO2S harness connector and PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2, Fig 1, Figure and Figure . If all resistance measurements are less than 5 ohms, go to next step. If any resistance measurement is 5 ohms or more, repair open in affected circuit.
    49. NOTE: HO2S may be displayed as O2S on scan tool.

  49. 85) Check HO2S Circuit Voltage
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Reconnect suspect HO2S and PCM harness connectors. Turn ignition switch to ON position. Using scan tool, access suspect HO2S PID (12 or 22) from PID/DATA MONITOR & RECORD menu. HO2S DTC identification is as follows:
    • DTCs P0136, P1137 and P1138 are for HO2S-12.
    • DTCs P0156, P1157 and P1158 are for HO2S-22.

    Refer to illustrations for HO2S identification. See Figure-Figure . If HO2S PID voltage is more than 1.5 volts, go to step  88). If HO2S PID voltage is 1.5 volts or less, go to next step.

  50. 86) Check HO2S Ground Circuit In PCM

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance between PWR GND and SIG RTN circuits at PCM connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2 or Fig 1 . If resistance measurement is less than 5 ohms, go to next step. If resistance measurement is 5 ohms or more, replace PCM.

  51. 87) HO2S Circuit Check

    Ensure ignition switch is turned to OFF position. Reconnect PCM harness connector(s). Disconnect suspect HO2S connector. Connect a jumper wire between VPWR and HO2S SIG circuits at suspect HO2S harness connector. See Figure or Figure . Turn ignition switch to ON position. Using scan tool, access suspect HO2S PID (12 or 22) from PID/DATA MONITOR & RECORD menu. If suspect HO2S PID voltage is more than 1.5 volts, replace faulty HO2S. If suspect HO2S PID voltage is 1.5 volts or less, replace PCM.

  52. 88) Check For Over Voltage On HO2S Circuit In PCM

    Turn ignition switch to OFF position. Disconnect suspect HO2S connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal and HO2S SIG and SIG RTN circuits at suspect HO2S harness connector. See Figure or Figure . If either voltage measurement is more than 1.5 volts, replace PCM. If both voltage measurements are 1.5 volts or less, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 88) to step 100). No test procedures have been omitted.
    53. NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 100) to step 110). No test procedures have been omitted.

  53. 100) KOER DTC P1127
    Service all other DTCs before proceeding with this test. DTC P1127 indicates that downstream HO2S heaters were cycled ON during KOER self-test and exhaust temperatures were below a minimum calibrated value. Possible causes are:
    • Engine Not At Operating Temperature
    • Exhaust System Too Cool

    Connect scan tool to Data Link Connector (DLC). Using scan tool, access all HO2S HTR PIDs and HO2S monitor PIDs from PID/DATA MONITOR & RECORD menu. If all HO2S PIDs switch or indicate ON, perform KOER ON-DEMAND SELF-TEST . If any HO2S PIDs indicate OFF or do not switch, operate engine until all HO2S PIDs indicate ON. Repeat KOER ON-DEMAND SELF-TEST .

    54. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  54. 110) KOER DTCs P1128 & P1129
    These DTCs indicate that during KOER self-test, HO2S signal response for a fuel shift corresponds to incorrect bank (cross between banks). DTC P1128 refers to upstream (fuel control) HO2S-11 or HO2S-21. DTC P1129 refers to downstream (catalyst monitor) HO2S-12 or HO2S-22. Possible causes for these faults are:
    • Crossed HO2S Connectors
    • Crossed HO2S Wiring At HO2S Connector
    • Crossed HO2S Wiring At PCM Connector

    Turn ignition switch to OFF position. Inspect HO2S wiring harness and connector for indication of being crossed (stretched wires or wire harnesses incorrectly installed). Repair as necessary. If no faults are found, go to next step.

  55. 111) Verify Proper HO2S SIG Terminal Location

    Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Disconnect both suspect HO2S harness connectors. HO2S DTC identification is as follows:
    • DTC P1128 is for upstream HO2S-11 and HO2S-21.
    • DTC P1129 is for downstream HO2S-12 and HO2S-22.

    Refer to illustrations for HO2S identification. See Figure-Figure . Using a DVOM, measure resistance of HO2S SIG circuit between suspect HO2S harness connector and PCM harness connector. See PCM HO2S, PWR GND & VPWR CIRCUIT TERMINAL IDENTIFICATION  table. See Fig 2, Fig 1, Figure and Figure . If resistance is less than 5 ohms, fault is intermittent and cannot be duplicated at this time. Go to TEST Z, step 1) . If resistance is 5 ohms or more, HO2S wiring is crossed. Recheck all HO2S wiring terminal locations at PCM and HO2S connectors. Repair as necessary.

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 111) to step 115). No test procedures have been omitted.
    56. NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: HO2S may be displayed as O2S on scan tool.

  56. 115) KOEO, KOER & Continuous Memory DTC P0132, P0138, P0152 Or P0158: Check HO2S Circuit Voltage
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Visually inspect HO2S circuit for exposed wiring, water contamination, corrosion and proper installation. On some applications, a hoist is required to access HO2S harness. Start engine and allow to idle. Using scan tool, access suspect HO2S PIDs. HO2S DTC identification is as follows:
    • DTC P0132 refers to upstream HO2S-11.
    • DTC P0138 refers to downstream HO2S-12.
    • DTC P0152 refers to upstream HO2S-21.
    • DTC P0158 refers to downstream HO2S-22.

    If HO2S PID voltage is 1.5 volt or more, go to next step. If HO2S PID voltage is less than 1.5 volt, concern may be intermittent. Attempt to duplicate concern, perform wiggle test on suspect circuit harness and component. If concern was duplicated, perform this pinpoint test again. If concern was not duplicated, go to TEST Z, step 1) .

  57. 116) Check HO2S For Short To PWR Inside Of Sensor

    Turn ignition switch to OFF position. Disconnect suspect HO2S connector. Turn ignition switch to ON position. Using scan tool, access suspect HO2S PID. If HO2S PID voltage is .5 volt or more, go to next step. If HO2S PID voltage is less than .5 volt, replace internally shorted HO2S sensor.

  58. 117) Check HO2S SIG Circuit For Short To PWR In Harness

    Turn ignition switch to OFF position. Ensure suspect HO2S is disconnected. Disconnect PCM connector(s). Using a DVOM, measure resistance between HO2S SIG circuit, and both VPWR and VREF circuits at PCM harness connector. If all resistance measurements are more than 10 k/ohms, replace PCM. If any resistance measurement is 10 k/ohms or less, repair short to PWR in affected circuits.
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