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Test Ha: Natural Gas Fuel Control: Testing

NOTE: Test procedure begins with step 30). No test procedures have been omitted.
NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION  table of fault code setting condition.
FAULT CODE SETTING CONDITION

Fault Code KOEO KOER Continuous Memory
P0040    HA100  
P0041    HA100  
P0135  HA30  HA30  HA30
P0141  HA30  HA30  HA30
P0155  HA30  HA30  HA30
P0161  HA30  HA30  HA30
P0171      HA41
P0172      HA41
P0174      HA41
P0175      HA41
P1127    HA90  
P1128    HA100  
P1129    HA100  
P1130      HA40
P1131    HA40  HA40
P1132    HA40  HA40
P1150      HA40
P1151    HA40  HA40
P1152    HA40  HA40
P2195    HA40  HA40
P2196    HA40  HA40
P2197    HA40  HA40
P2198    HA40  HA40
    NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  1. 30) For KOEO, KOER & Continuous Memory DTCs P0135, P0141, P0155 Or P0161: HO2S HTR SIG Circuit Is Open, Shorted To Ground Or VPWR, Or Excessive 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 Refers To Upstream HO2S-11
    • DTC P0141 Refers To Downstream HO2S-12
    • DTC P0155 Refers To Upstream HO2S-21
    • DTC P0161 Refers To Downstream HO2S-22

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

    • Short To VPWR Or HO2S Circuit
    • 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 connectors for loose, damaged or corroded terminals. Repair as necessary. If HO2S connectors are okay, go to next step.

  2. 31) Perform KOEO 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 DTCs P0135, P0141, P0155 and/or P0161 are present, go to next step. If specified DTCs are not present, fault may be intermittent. Go to TEST Z, step 1) .
    3. 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.

  3. 32) Check VPWR Voltage To HO2S Harness Connector
    Turn ignition switch to OFF position. Disconnect suspect HO2S connector. 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. If voltage is 10.5 volts or less, go to next step. If voltage is more than 10.5 volts, go to step  34).

  4. 33) Check VPWR Circuit For Open In Harness

    Turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of VPWR circuit between PCM harness connector and HO2S harness connector. See NGV HO2S PCM TERMINAL IDENTIFICATION  table. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, check VPWR circuit fuse. If fuse is okay, repair open in VPWR circuit.

  5. 34) Check HO2S HTR Resistance

    Turn ignition switch to OFF position. Using a DVOM, measure resistance of HO2S HTR GND and VPWR terminals at HO2S connector. See Figure. If resistance is 3-30 ohms, go to next step. If resistance is not 3-30 ohms, replace faulty HO2S.

  6. 35) Check HO2S Case For Short To HTR GND Or VPWR

    Using a DVOM, measure resistance between HO2S case and HO2S HTR GND and VPWR terminals at HO2S connector. See Figure. If both resistance measurements are more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, replace faulty HO2S.

  7. 36) Check For Shorts To Other Grounds Or VPWR In HO2S HTR GND Harness Circuits

    Disconnect PCM connector. Using a DVOM, measure resistance between HO2S HTR circuit, and PWR GND, SIG RTN and VPWR circuits at suspect HO2S harness connector. See 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 between affected circuits.

  8. 37) Check HO2S HTR GND For Open In Harness

    Using a DVOM, measure resistance of HO2S HTR GND circuit between suspect HO2S harness connector and PCM harness connector. See NGV HO2S PCM TERMINAL IDENTIFICATION  table. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open or excessive resistance in HTR GND circuit in wiring harness.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 37) to step 40). No test procedures have been omitted.
    9. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  9. 40) For Continuous Memory Only DTCs P1130, P1150, & For KOER & Continuous Memory DTCs P1131, P1132, P1151, P1152, P2195, P2196, P2197 Or P2198: Upstream HO2S Not Switching
    Continuous Memory DTCs P1130 and P1150 indicate when an HO2S fails to switch due to a circuit or fuel at or exceeding a calibrated limit. KOER and Continuous Memory DTCs P1131, P1132, P1151, P1152, P2195, P2196, P2197 and P2198 indicate a concern when fuel control system does not detect HO2S switching for a calibrated time. DTCs P1130, P1131, P1132, P2195 and P2196 refer to HO2S-11. DTCs P1150, P1151, P1152, P2197 and P2198 refer to HO2S-21. 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, 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) .

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

  10. 41) For Continuous Memory Only DTC P0171, P0172, P0174 Or P0175: Fuel System At Corrected Fuel Trim
    DTCs P0171, P0172, P0174 and P0175 indicate a concern when adaptive fuel strategy senses a lean or rich condition beyond the minimum or maximum calibrated limit. DTCs P0171 (lean) and P0172 (rich) refer to bank No. 1. DTCs P0174 (lean) and P0175 (rich) refer to bank No. 2. 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) .

  11. 42) Perform KOER Self-Test

    Perform KOER ON-DEMAND SELF-TEST . If KOER DTC P1131, P1132, P1151, P1152 P2195, P2196, P2197 or P2198 is present, go to next step. If none of these DTCs are present, proceed as follows:
    • For Continuous Memory DTCs P0171, P0172, P0174, P0175, P1130 or P1150, go to next step.
    • For any other DTCs, fault may be intermittent. Go to TEST Z, step 1) .
    12. WARNING: Fuel system remains under high pressure even when engine is not running. To avoid injury, release fuel pressure before disconnecting any fuel system hose or component. See FUEL SYSTEM PRESSURE RELEASE procedure under FUEL SYSTEM VENTING in appropriate REMOVAL & INSTALLATION article.
    NOTE: Not all natural gas vehicles are equipped with Fuel Rail Pressure (FRP) sensor. On vehicles without FRP sensor, use values supplied by fuel rail pressure gauge.

  12. 43) Check Fuel Pressure
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Install Natural Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail Schrader valve. Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. With ignition switch turned to ON position, record FRP sensor PID or fuel pressure gauge reading. Start engine and allow to idle. Again record FRP sensor PID or fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. Record FRP sensor PID or fuel pressure gauge reading. If fuel pressure readings are 80-120 psi (552-827 kPa), turn ignition switch to OFF position and go to next step. If fuel pressure readings are not 80-120 psi (552-827 kPa), turn ignition switch to OFF position and go to TEST HB, step  1).

  13. 44) Check Fuel System For Pressure Stability

    With fuel pressure gauge installed, cycle ignition switch from OFF to ON position 2 times to pressurize fuel system (DO NOT start engine). Verify no external leaks are present. If fuel pressure does not remain within 10 psi (69 kPa) of highest fuel pressure reading after 2 minutes, go to TEST HB, step  1). If fuel pressure remains within 10 psi (69 kPa) of highest fuel pressure reading after 2 minutes, proceed as follows:
    • If DTCs P1130, P1150, P0171 P0172, P0174 and P0175 are present or engine is a no-start, go to next step.
    • If engine does not start, go to next step.
    • If any other DTC is present, go to step  62).

  14. 45) Check Fuel System For Pressure Stability With Ignition Switch Turned To ON Position

    Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. If FRP PID is not available, install Natural Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail Schrader valve. Cycle ignition switch from OFF to ON (DO NOT start engine). Monitor fuel pressure reading. If fuel pressure does not remain within 10 psi (69 kPa) of highest fuel pressure reading after 10 seconds, go to step  56). If fuel pressure remains within 10 psi (69 kPa) of highest fuel pressure reading after 10 seconds, proceed as follows:
    • If engine is a no-start, go to next step.
    • For DTCs P1130, P1150, P0171 and P0174, go to step  55).

  15. 46) Check Fuel Injectors Ability To Deliver Fuel

    Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. If FRP PID is not available, install Natural Gas Fuel Rail Pressure Gauge Tool Kit (134-00114) to fuel rail Schrader valve. Cycle ignition switch from OFF to ON position 2 times to pressurize fuel system (DO NOT start engine). Record fuel pressure reading. Locate and disconnect Inertia Fuel Shutoff (IFS) switch. Crank engine for 10 seconds. If fuel pressure reading remains within 10 psi (34 kPa) of original pressure reading, go to next step. If fuel pressure drops more than 10 psi (34 kPa) from original pressure reading, EEC-V system is not the cause of no-start. Diagnose no-start symptom. See NO-START/NORMAL CRANK under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article.

  16. 47) Check VREF Voltage At Natural Gas Module

    Turn ignition switch to OFF position. Install NG module breakout box. For NG module location, see NATURAL GAS MODULE LOCATION  table. Connect NG module. Turn ignition switch to ON position. Using a DVOM, measure voltage between VREF and SIG RTN circuits at NG module breakout box. See Figure. If voltage is 4-6 volts, go to next step (no-starts), or go to step  57) (all others). If voltage is not 4-6 volts, turn ignition switch to OFF position and go to step  50).
    NATURAL GAS MODULE LOCATION

    Application Location
    Crown Victoria Front Of Radiator Support
    Econoline On Left Side Of Inner Fender Panel In Engine Compartment
    F150 Pickup On Right Front Side Of Engine Compartment

  17. 48) Check For Open In PWR GND Circuit

    Turn ignition switch to OFF position. Disconnect NG module 60-pin connector. Using a DVOM, measure resistance of PWR GND circuit between NG module harness connector and negative battery terminal. See Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in PWR GND circuit.

  18. 49) Check For Open In PWR GND Circuit In NG Module

    Turn ignition switch to OFF position. Disconnect NG module 60-pin connector. Measure resistance between PWR GND and SIG RTN circuits at NG module. See Figure. If resistance is 5 ohms or more, replace NG module. If resistance is less than 5 ohms, go to step  57) (no-starts), or reconnect PCM and NG module and go to TEST A, step 6) (all others).

  19. 50) Is VREF More Than 6 Volts

    If voltage in step  47) was 6 volts or less, go to next step. If voltage was more than 6 volts, go to step  55).

  20. 51) Check Battery Voltage

    Using a DVOM, measure voltage across battery terminals. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check charging system and battery. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. Repair as necessary.

  21. 52) Check VPWR At NG Module

    Turn ignition switch to ON position. Using a DVOM, measure voltage between PWR GND and VPWR circuits at NG module connector. See Figure. If voltage is 10.5 volts or less, go to next step. If voltage is more than 10.5 volts, go to step  54).

  22. 53) Check Voltage Between VPWR At NG Module & Battery Ground

    Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal and VPWR circuit at NG module connector. See Figure. If voltage is 10.5 volts or less, repair open in VPWR circuit between NG module and PCM power relay. If voltage is more than 10.5 volts, repair open in PWR GND circuit.

  23. 54) Check VREF Voltage To Fuel Tank Pressure Sensor

    Turn ignition switch to OFF position. Locate and disconnect Fuel Tank Pressure (FTP) sensor connector. See FUEL TANK PRESSURE SENSOR LOCATION  table. Turn ignition switch to ON position. Using a DVOM, measure voltage between SIG RTN and VREF circuits at FTP sensor harness connector. See Figure. If voltage is 4-6 volts, replace FTP sensor. See FUEL TANK PRESSURE SENSOR under FUEL SYSTEMS in appropriate REMOVAL & INSTALLATION article. If voltage is not 4-6 volts, go to step  56).
    FUEL TANK PRESSURE SENSOR LOCATION

    Application Location
    Crown Victoria Under Vent Box Cover Of Upper Fuel Tank Assembly
    Econoline Under Left Side Center Of Vehicle
    F150 Pickup Part Of Fuel Pump Assembly

  24. 55) Check VREF Circuit For Short To PWR In Harness

    Turn ignition switch to OFF position. Disconnect NG module and FTP sensor connectors. Turn ignition switch to ON position. Using a DVOM, measure voltage between PWR GND and VREF circuits at NG module harness connector. See Figure. If voltage is less than one volt, replace NG module. If voltage is one volt or more, repair short to PWR in VREF circuit.

  25. 56) Check VREF Circuit For Short To PWR GND

    Turn ignition switch to OFF position. Disconnect NG module connector. Using a DVOM, measure resistance between VREF circuit and the SIG RTN, PWR GND and CASE GND circuits at the NG module harness connector. See Figure. If all resistance measurements are more than 10 k/ohms, replace NG module. If any resistance measurement is 10 k/ohms or less, repair short to ground in VREF circuit.

  26. 57) Check Fuel Injectors & Harness Resistance From NG Module To Fuel Injectors

    Ensure fuel injector harness connectors are connected. Leave ignition switch turned to OFF position and NG module disconnected. Using a DVOM, measure resistance between VPWR circuit and suspect fuel injector circuit at NG module harness connector. See NG MODULE FUEL INJECTOR CIRCUIT TERMINAL IDENTIFICATION  table. See Figure. If resistance is 3-6 ohms, go to step  60). If resistance is not 3-6 ohms, go to next step.
    NG MODULE FUEL INJECTOR CIRCUIT TERMINAL IDENTIFICATION

    Cylinder No. NG Module Injector Circuit Terminal No.
    1 58
    2 59
    3 39
    4 35
    5 33
    6 42
    7 53
    8 54

  27. 58) Check Fuel Injector Harness Resistance Between NG Module & Fuel Injector

    Disconnect suspect fuel injector harness connector. Using a DVOM, measure resistance of injector and VPWR circuits between suspect fuel injector harness connector and NG module harness connector. See Figure. If both 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.

  28. 59) Check Fuel Injector Harness Circuit For Short To PWR Or Ground Between NG Module & Injectors

    Ensure suspect fuel injector harness connector is disconnected. Using a DVOM, measure resistance between suspect injector circuit, and PWR GND and VPWR circuits at NG module harness connector. See NG MODULE FUEL INJECTOR CIRCUIT TERMINAL IDENTIFICATION  table. See Figure. If any resistance measurement is 10 k/ohms or less, repair short between circuits. If all resistance measurements are more than 10 k/ohms, go to step  61) (DTC P0172 or P0175), or replace faulty fuel injector(s) (all others).
    29. NOTE: A properly operating system will show a dim glow at idle on 12-volt test light.

  29. 60) Check Fuel Injector Driver Signal
    Ensure ignition switch is turned to OFF position. Connect NG module harness connector. Connect 12-volt test light between injector and VPWR circuits at suspect fuel injector harness connector. While cranking engine, observe test light. If test light does not glow dimly (no light or continuous bright light) while cranking or running engine, go to next step. If test light glows dimly, PCM and NG module circuits are okay. If engine runs rough, see ROUGH OR ROLLING IDLE, STALLS, MISSES, HESITATION OR SURGE under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If engine is a no-start, go to TEST A, step 4) . For all others, go to step  64).

  30. 61) Check PCM Fuel Injector Harness Circuit Resistance

    Ensure ignition switch is turned to OFF position. Ensure NG module and PCM harness connectors are disconnected. Using a DVOM, measure resistance of VPWR circuit and injector circuits between PCM harness connector and NG module harness connector. See PCM TO NG MODULE TERMINALS  table. See PCM CONNECTOR IDENTIFICATION 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.
    PCM TO NG MODULE TERMINALS

    Application PCM Terminal No. NG Module Terminal No.
    Fuel Injector No. 1 75 3
    Fuel Injector No. 2 101 4
    Fuel Injector No. 3 74 5
    Fuel Injector No. 4 100 23
    Fuel Injector No. 5 73 24
    Fuel Injector No. 6 99 25
    Fuel Injector No. 7 72 43
    Fuel Injector No. 8 98 44
    PWR GND 24, 51, 76, 77 & 103 40 & 60
    VPWR 71 & 97 37 & 57

  31. 62) Check PCM Fuel Injector Circuit For Short To PWR Or GND In Harness

    Using a DVOM, measure resistance between injector circuits, and PWR GND and VPWR circuits at PCM harness connector. Using a DVOM, measure resistance between injector circuits, and CASE GND, PWR GND and VPWR circuits at NG module harness connector. See PCM TO NG MODULE TERMINALS  table. See PCM CONNECTOR IDENTIFICATION and Figure. If any resistance measurement is 10 k/ohms or less, repair short between affected circuits. If all resistance measurements are more than 10 k/ohms, go to step  64) (DTCs P0172 and P0175), or go to next step (all others).

  32. 63) Check Fuel Injector Driver Signal From PCM

    Ensure ignition switch is turned to OFF position. Connect PCM harness connector. Ensure NG module is disconnected. Connect 12-volt test light between VPWR circuit and each fuel injector signal circuit from PCM at NG module harness connector. See Figure. Crank engine and observe test light. If test light does not glow dimly or flicker, replace PCM. If test light glows dimly or flickers, engine runs okay or you were directed here for DTCs, go to next step. If test light glows dimly or flickers and engine is a no-start, replace NG module. If test light glows dimly or flickers and engine runs rough, diagnose by symptom. See ROUGH OR ROLLING IDLE, STALLS, MISSES, HESITATION OR SURGE under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article.

  33. 64) Check Fuel Injector Flow & Leakage

    Turn ignition switch to OFF position. Reconnect all connectors. Connect scan tool to Data Link Connector (DLC). Install electronic Natural Gas Injector Tester found in Natural Gas Tool Kit (134-00114) to suspect fuel injector. Follow injector tester instructions and specifications. Turn ignition switch to ON position. Using scan tool, access FRP PID (if available) from PID/DATA MONITOR & RECORD menu. Record initial FRP sensor PID or fuel pressure gauge reading. Using scan tool, access pulse width of 200 milliseconds. Activate fuel injector tester. Record final FRP sensor PID or fuel pressure gauge reading. Subtract final FRP sensor PID or fuel pressure gauge reading from the initial reading to calculate pressure drop. Repeat test procedures for all injectors. If fuel injector flow or leakage rate is not within specification, replace defective fuel injector(s). If flow rate or leakage is within specification for each fuel injector, proceed as follows:
    • If directed here for DTCs P0171, P0172, P0174 and P0175, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .
    • If directed here for DTCs P1130 and P1150, go to step  66).
    • For all others, go to next step.

  34. 65) Check Cylinder Compression

    Using compression gauge, check compression on all cylinders. Record cylinder compressions. Cylinder compressions should be higher than 75 percent of highest cylinder compression reading. If a cylinder's compression is not within specification, repair engine as necessary. If all cylinder compressions are within specification, go to next step (DTCs P1130, P1131, P1150, P1151, P2195 and P2197), or go to step  71) (DTCs P1132, P1152, P2196 or P2198).

  35. 66) Check HO2S Integrity

    Turn ignition switch to OFF position. Inspect HO2S and wiring harness for chafing, damage and contamination from oil, water, coolant, etc. Repair as necessary. If no visible concerns are found, start engine and operate at 2000 RPM for 2 minutes. Using scan tool, perform KOER ON-DEMAND SELF-TEST . Turn ignition switch to OFF position. If DTC P1131, P1151, P2195 and/or P2197 is present, go to next step. If DTC P1131, P1151, P2195 and/or P2197 is not present, HO2S system is functioning properly at this time. Faults cannot be duplicated or identified at this time. Go to TEST Z, step 1) .
    36. NOTE: Vacuum or air leaks can cause DTCs P1130, P1131, P1150, P1151, P2195 and P2197 to set.

  36. 67) Check HO2S Ability To Generate A Voltage More Than .5 Volt
    Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector. Using a DVOM, measure voltage between HO2S SIG circuit, and SIG RTN or HO2S GND circuits at HO2S connector. See Figure. Start engine and operate at 2000 RPM for 2 minutes. Repeat KOER ON-DEMAND SELF-TEST while monitoring HO2S voltage. If voltage measurement is more than .5 volt during, or at end of test, go to next step. If voltage measurement stays at .5 volt or less during test, replace HO2S.

  37. 68) Check HO2S SIG & SIG RTN Circuits For Open In Harness

    Turn ignition switch to OFF position. Disconnect PCM connector. Disconnect suspect HO2S harness connector. Inspect both ends of connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of HO2S SIG and SIG RTN circuits between PCM harness connector and suspect HO2S harness connector. See NGV HO2S PCM TERMINAL IDENTIFICATION  table. See PCM CONNECTOR IDENTIFICATION and 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 affected circuit.

  38. 69) Check HO2S Circuit For Short To Ground In Harness

    Using a DVOM, measure resistance of HO2S SIG circuit between PCM harness connector and negative battery terminal. See NGV HO2S PCM TERMINAL IDENTIFICATION  table. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in HO2S SIG circuit.

  39. 70) Check HO2S Circuit For Short To Ground

    Using a DVOM, measure resistance between suspect HO2S SIG circuit, and PWR GND or SIG RTN circuits at PCM harness connector. If either resistance measurement is 10 k/ohms or less, replace HO2S. If both resistance measurements are more than 10 k/ohms, proceed as follows:
    • For DTCs P1130 and P1150, go to next step.
    • For Continuous Memory DTCs P1131, P1151, P2195 and P2197, go to step  76).
    • For KOER DTCs P1131, P1151, P2195 and P2197, replace PCM.

  40. 71) Check For DTCs P1132, P1152, P2196 & P2198 With P1130 & P1150

    Perform KOER ON-DEMAND SELF-TEST . If DTC P1132, P1152, P2196 or P2198 is present, go to next step. If DTC P1132, P1152, P2196 or P2198 is not present, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .
    41. NOTE: HO2S may be displayed on scan tool as O2S.

  41. 72) Check HO2S SIG Circuit For Short To VPWR & VREF
    DTCs P1130, P1132, P2196 (HO2S-11) and/or P1150, P1152, P2198 (HO2S-21) indicate HO2S is always rich. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, access appropriate HO2S PID for DTC retrieved. If HO2S PID voltage is more than one volt and less than 4 volts, go to next step. If HO2S PID voltage is not as specified, go to step  75).

  42. 73) Check HO2S Circuit For Short To VPWR

    Turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Disconnect suspect HO2S connector. Using a DVOM, measure resistance between HO2S SIG and VPWR circuits at suspect HO2S harness connector. See Figure. If resistance measurement is more than 10 k/ohms, reconnect PCM and go to next step. If resistance measurement is 10 k/ohms or less, repair short to VPWR.
    43. NOTE: HO2S may be displayed on scan tool as O2S.

  43. 74) Check HO2S SIG For Short To HO2S HTR Circuit In Sensor
    Ensure scan tool is connected to DLC. Ensure suspect HO2S is disconnected. Turn ignition switch to ON position. Using scan tool, access HO2S PID for DTC retrieved. If HO2S PID voltage is less than .2 volt, replace internally shorted HO2S. If HO2S PID voltage is .2 volt or more, replace PCM.

  44. 75) Attempt To Generate DTCs P1131, P1151, P2195 & P2197

    Disconnect suspect HO2S connector. Connect a jumper wire between HO2S SIG circuit at HO2S harness connector and negative battery terminal. See Figure. Perform KOER ON-DEMAND SELF-TEST . If DTC P1131, P1151, P2195 or P2197 is present, remove jumper wire and go to next step. If DTC P1131, P1151, P2195 or P2197 is not present, disconnect and inspect PCM connector and harness connector terminals and repair as necessary. If PCM connector and harness connector terminals are okay, replace PCM.

  45. 76) HO2S Voltage Check

    Disconnect HO2S connector. Connect DVOM between HO2S SIG and SIG RTN circuits at HO2S harness connector. Disconnect any vacuum hose from vacuum tree. Start engine and operate at 2000 RPM. If DVOM voltage is less than .4 volt within 30 seconds, reconnect vacuum hose and reconnect all connectors. Go to next step. If DVOM voltage is .4 volt or more after 30 seconds, replace HO2S.
    46. NOTE: HO2S PID may be displayed on scan tool as O2S.

  46. 77) Monitor HO2S PID For Proper Switching
    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 HO2S PID for DTC retrieved. Observe HO2S PID voltage while wiggling and bending small sections of wiring harness from HO2S to PCM. If HO2S PID voltage stays high (more than .45 volt) or stays low (less than .45 volt), isolate cause of lack of HO2S switches. Repair as necessary. If HO2S PID voltage switches, go to next step.

  47. 78) Test Drive While Monitoring HO2S PID For Proper Switching

    Using an assistant, test drive vehicle under various conditions while assistant observes suspect HO2S PID. If suspect HO2S PID voltage switches properly, system is okay at this time and testing is complete. If voltage does not switch properly, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 78) to step 90). No test procedures have been omitted.
    48. NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 90) to step 100). No test procedures have been omitted.

  48. 90) For KOER Only DTC P1127
    DTC P1127 indicates that downstream HO2S heaters were not cycled on during KOER self-test due to exhaust temperatures falling 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 HO2S HTR-11 & HO2S HTR-21 PIDs from PID/DATA MONITOR & RECORD menu. If both HO2S HTR PIDs indicate ON, perform KOER ON-DEMAND SELF-TEST while engine is still running to verify P1127 is no longer present. If either HO2S HTR PID indicates OFF, operate engine until all HO2S HTR PIDs indicate ON. Repeat KOER ON-DEMAND SELF-TEST .

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

  49. 100) For KOER Only DTCs P0040, P0041, P1128 & P1129
    These DTCs indicate that during KOER self-test, HO2S signal response for a fuel shift corresponded to incorrect bank (cross between banks). DTC P1128 refers to upstream HO2S-11 or HO2S-21. DTC P1129 refers to downstream 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. Disconnect suspect HO2S harness connector. Inspect connector for indication of crossed or stretched wires or wire harnesses incorrectly installed. Repair as necessary. If no faults are found, go to next step.

  50. 101) Verify Proper HO2S SIG Terminal Location

    Disconnect PCM connector. 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 NGV HO2S PCM TERMINAL IDENTIFICATION  table. See PCM CONNECTOR IDENTIFICATION and Figure. If resistance is less than 5 ohms, HO2S SIG circuit is okay. Fault is intermittent and cannot be duplicated at this time. 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.

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