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Home >> Ford >> 1995 >> Mustang Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - EEC-V (3.8L) >> Circuit Tests >> Circuit Test DH - Throttle Position (TP) Sensor >> Diagnostic Aids
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Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:

Normal range of throttle angle measurement for TP sensor is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification.

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault:

Fig 1: TP Sensor Schematic
G94J32549
Fig 2: Identifying TP Sensor Circuit & Connector Terminals
G94D32550

1) KOEO/KOER DTC P1124: Check For Other Codes  DTC P1124 indicates TP sensor rotational setting may be out of self-test range. Possible causes for this fault are:

Perform KOEO and KOER self-test. Check for DTC P1400. If DTC P1400 is present, service code and repeat QUICK TEST. If DTC P1400 is not present with DTC P1124, go to step 2).

2) DTC P1120: Check For Binding Throttle Plate  DTC P1120 indicates TP sensor is below closed throttle position range of 9.8 percent (.49 volt) Possible causes for this fault are:

Inspect throttle body for binding. If throttle body is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference. Repair as necessary, and repeat QUICK TEST. If no mechanical problem is found, go to step 3).

3) Check For Stuck TP Sensor  Turn ignition off. Connect scan tester to DLC. Access TP PID on scan tester. While observing TP PID, slowly move throttle through range from closed to wide open throttle. If TP PID indicates any sudden drops to below 0.49 volt, replace TP sensor and repeat QUICK TEST. If TP PID increase and decrease is gradual and smooth, go to next step.

4) Check TP Sensor Signal To PCM  Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged and repair as necessary. Install EEC-V Breakout Box (014-00950). Connect PCM to breakout box. Start engine and idle for 2 minutes. While slowly opening throttle, measure voltage between test pin No. 89 (TP) and 91 (SIG RTN) at breakout box. If at any time voltage enters 0.17-0.40 volt range, replace TP sensor. If voltage does not enter 0.17-0.40 volt range, go to next step.

5) DTC P0123  This code indicates TP signal is more than self-test maximum. Possible causes for this fault are:

Turn ignition off. Disconnect TP sensor wiring harness connector. Inspect for damage and repair as necessary. Turn ignition on. Access TP PID on scan tester. If PID voltage is 0.17 volt or more, go to step 7). If PID voltage is less than 0.17 volt, go to next step.

6) Check VREF Circuit Voltage  With TP sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If voltage is 4-6 volts, replace TP sensor and repeat QUICK TEST. If voltage is not 4-6 volts, reconnect sensor and go to CIRCUIT TEST C.

7) Check TP Circuit For Short To Power  Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 89 (TP) and test pins No. 71, 90 and 97 (VPWR) at breakout box. If any resistance is less than 10,000 ohms, repair TP circuit short to VREF and repeat QUICK TEST. If each resistance is 10,000 ohms or more, replace PCM and repeat QUICK TEST. 8) DTC P0122

This code indicates TP signal is less than self-test minimum of 0.17 volt. Possible causes for this fault are:

Turn ignition off. Disconnect TP sensor wiring harness connector. Inspect for damage and repair as necessary. Connect jumper wire between VREF and TP terminals at TP wiring harness connector. Turn ignition on. Access TP PID on scan tester. If PID voltage is more than 4.60 volts, replace TP sensor and repeat QUICK TEST. If PID voltage is 4.60 volts or less, go to next step. If scan tester is unable to access TP PID, go to step 11).

9) Check VREF Circuit Voltage  With TP sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If reading is 4-6 volts, go to next step. If reading is not 4-6 volts, reconnect sensor and go to CIRCUIT TEST C.

10) Check TP Circuit Continuity  Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 89 (TP) and TP terminal of TP sensor wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in TP circuit.

11) Check TP Circuit For Short To SIG RTN Or PWR GND  Leave ignition off and TP sensor disconnected. Measure resistance between test pin No. 89 (TP) and test pins No. 91 (SIG RTN), 24 and 103 (PWR GND) at breakout box. If any resistance is less than 10,000 ohms, repair TP circuit short to SIG RTN or PWR GND and repeat QUICK TEST. If both resistances are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

12) Continuous Memory Code P1121  This code indicates TP signal is inconsistent with MAF sensor signal. Possible causes for this fault are as follows:

If engine will start, go to next step. If engine is a no-start, check for cracks or openings in air induction system between MAF sensor and throttle body. If air induction system is okay, go to CIRCUIT TEST A.

13) Check Operation Of TP Sensor  Start engine and allow to idle. Access TP PID on scan tester. While observing TP PID, slowly move throttle through range from closed position to wide open throttle. If TP PID indicates any sudden drops to below 0.66 volt, or increases to more than 1.20 volts, replace TP sensor and repeat QUICK TEST. If TP PID increase and decrease is gradual and smooth, and within 0.66-1.20 volt range, go to next step.

14) Check Operation Of TP Sensor While Driving Vehicle  Connect scan tester to DLC. Drive vehicle while accessing TP PID and LOAD PID. If TP PID is 2.44 volts or less and LOAD PID is more than 25 percent, go to next step. If TP PID is more than 2.44 volts and LOAD PID is less than 25 percent, check for cracks or openings in air induction system between MAF sensor and throttle body. If air induction system is okay, replace TP sensor.

15) Check TP Sensor Low With Engine Under Load  Start engine and allow to idle. If engine does not start, go to CIRCUIT TEST A. Access TP PID and LOAD PID on scan tester. If TP PID is 0.24 volt or more and LOAD PID is less than 60 percent, go to next step. If TP PID is less than 0.24 volts and LOAD PID is 60 percent or more, clear PCM memory. Perform test drive utilizing all phases of vehicle operation. Perform QUICK TEST. If DTC P1121 is still present, replace MAF sensor.

16) Check Operation Of TP Sensor While Driving Vehicle  Connect scan tester to DLC. Drive vehicle while accessing TP PID and LOAD PID. If TP PID is 0.24 volt or less and LOAD PID is more than 60 percent, go to next step. If TP PID is more than 0.24 volt and LOAD PID is less than 60 percent, problem is intermittent and cannot be identified at this time. If vehicle will not start, go to CIRCUIT TEST A.

17) Continuous Memory Code P1125  This code indicates TP signal went below 0.49 volt or above 4.60 volts sometime during the last 80 drive cycles. Possible causes for this fault are:

With scan tester connected, start engine and allow to idle. Raise engine speed to 1500 RPM for 5 seconds and return to idle. Access TP PID. While observing PID, lightly tap on TP sensor to simulate road shock. Wiggle sensor connector and wiring harness. If TP PID reading stays within normal operating range (0.49-4.60 volts), go to next step. If TP PID reading goes out of range, replace TP sensor.

18) Check Wiring Harness Between TP Sensor & PCM  Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950). Connect PCM to breakout box. Connect DVOM between test pin No. 89 (TP) and 91 (SIG RTN). While observing DVOM, wiggle small sections of wiring harness starting at the TP sensor and going to the PCM. If DVOM reading stays within normal operating range (0.49-4.60 volts), problem is intermittent and cannot be identified at this time. If DVOM reading goes out of range, isolate fault and repair as necessary. Clear PCM memory and repeat QUICK TEST.

19) DTC PO121: Unable To Exit KOER Self-Test  Start engine and allow to idle. Using scan tester, enter KOER self test. If DTC P121 is present or KOER cannot be terminated, go to next step. If specified symptoms are not present, problem is intermittent and cannot be identified at this time.

20)  With engine idling, place gear selector in Drive or Reverse. If KOER self-test terminates, go to next step. If KOER self-test does not terminate, turn ignition off. Enter KOER self-test. If DTC P121 is present or KOER cannot be terminated, go to next step.

21) Check Circuit Continuity  Turn ignition off. Check continuity in TP circuit between TP sensor connector and PCM connector terminal No. 89. Check continuity in SIG RTN circuit between TP sensor connector and PCM connector terminal No. 91. If continuity is present, replace TP sensor and repeat QUICK TEST. If continuity is not present, repair open circuit and repeat QUICK TEST.

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