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Home >> Ford >> 2002 >> Taurus SES, 3.0 S >> Repair and Diagnosis >> External Pages >> Different car >> Section 194 (Engine Controls - Self-Diagnostics - 6.0L (99P F450/550) Diesel) >> System Tests >> Test Ag: Accelerator Pedal Position Sensor >> Testing

Test Ag: Accelerator Pedal Position Sensor: Testing

WARNING: This page is about a different car, the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, 2003 Ford Excursion, and 2003 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: The Powertrain Control Module (PCM) harness connectors must be properly seated and the connector latch properly attached to eliminate possible driveability concerns or a no-start condition. Installing PCM connectors on an angle may cause a bad connection, misdiagnosis and damaged components. Install the connector on where the lever pivots and seats itself. Apply light pressure to get the connector into position on the PCM lever to fully seat the connector.
NOTE: When the PCM engine harness connector is disconnected additional DTCs will be set. All DTCs must be cleared before returning the vehicle to service.

  1. 1) Preliminary Diagnosis

    Perform visual inspection. Connect the scan tool. Retrieve and record any continuous and on-demand DTCs. Record freeze frame data. Clear all DTCs. Perform the On-Demand Self-Test. Are any DTCs retrieved? If yes, proceed as follows:
    • For DTC P2122, P2127 or P2132, go to next step.
    • For DTC P2123, P2128 or P2133, go to step  8).
    • For DTC P2138, P2139 or P2140, go to step  13).

    If no, unable to duplicate condition. Check for loose connections, damaged or corroded pins. Wiggle harness attempting to recreate fault.

  2. 2) DTC P2122, P2127 Or P2132

    Possible causes are:
    • APP not seated correctly.
    • Faulty APP sensor.
    • Open in signal circuit.
    • Signal circuit shorted to ground.
    • Faulty PCM.

    Key on. Using scan tool, access PIDs APP1, APP2, APP3. Depress accelerator pedal while observing voltage reading on scan tool. Observe PID while pressing the accelerator pedal. Do all signal values change when the accelerator is depressed? If yes, unable to duplicate condition. Check for loose connections, damaged or corroded pins. Wiggle harness attempting to recreate fault. If no, go to next step.

  3. 3) Check VREF Sensor Circuits

    Key off. Disconnect the PCM body harness connector C1381A. Key on. Measure the voltage between APP harness connector terminals No. 4 and 9. See Figure. Is the voltage greater than 4.5-5.5 volts? If yes, go to next step. If no, repair open in VREF or PWR GND circuit. Restore the vehicle. Clear DTCs and retest the system.

  4. 4) Check Secondary VREF & Signal Return Circuits

    Measure the voltage between APP harness connector terminals No. 5 and 10. Is the voltage greater than 4.5-5.5 volts? If yes, go to next step. If no, repair open in secondary VREF or signal return circuit. Restore the vehicle. Clear DTCs and retest the system.

  5. 5) Check APP Sensor Signal For An Open

    Key off. Disconnect the PCM body harness connector C1381A. Measure the resistance of faulted signal circuit between the PCM body harness connector and APP harness connector. See CONTROL MODULE CONNECTOR IDENTIFICATION . Is the resistance less than 5.0 ohms? If yes, go to next step. If no, repair open in faulted APP signal circuit. Restore the vehicle. Clear DTCs and retest the system.

  6. 6) Check Faulted APP Sensor Signal For A Short To Ground

    Measure the resistance of the faulted signal circuit between the APP harness connector and ground. Is the resistance greater than 10,000 ohms? If yes, go to next step. If no, repair short to ground in faulted APP signal circuit. Restore the vehicle. Clear DTCs and retest the system.

  7. 7) Check APP Sensor Operation

    Connect the PCM body harness connector C1381A. Key on. Install a jumper wire between APP harness connector terminal No. 4 and faulted APP sensor circuit. Access APP PID values. Is the voltage of the faulted signal circuit 4.5-5.5 volts? If yes, install a new APP sensor assembly. Restore the vehicle. Clear DTCs and retest the system. If no, install a new PCM. Restore the vehicle. Clear DTCs and retest the system.

  8. 8) DTC P2123, P2128 Or P2133

    Possible causes are:
    • Signal shorted to voltage.
    • Signal return open.
    • Faulty APP sensor.
    • Faulty PCM.

    Key on. Using scan tool, access APP PID volts. Slowly depress the accelerator pedal while observing the voltage reading. Do all signal values change when the accelerator is depressed? If yes, unable to duplicate condition. Check for loose connections, damaged or corroded pins. Wiggle harness attempting to recreate fault. If no, go to next step.

  9. 9) Induce Opposite Failure

    Key off. Disconnect the APP sensor electrical connector. Using scan tool, access APP PID volts. Key on. Do all PID signal values read 0 volts? If yes, install a new APP sensor assembly. Restore the vehicle. Clear DTCs and retest the system. If no, go to next step.

  10. 10) Check APP Signal Circuits For A Short To Voltage

    Key off. Disconnect the PCM body harness connector C1381A. Key on. Measure the voltage of faulted signal circuit between the APP harness connector and ground. See Figure. Is the voltage less than 0.2 volt? If yes, go to next step. If no, repair short to voltage in faulted APP signal circuit. Restore the vehicle. Clear DTCs and retest the system.

  11. 11) Check APP Signal Circuits For A Short To Ground

    Key off. Measure the resistance of faulted signal circuit between the APP harness connector and ground. Is the resistance greater than 10,000 ohms? If yes, go to next step. If no, repair short to ground in the faulted signal circuit. Restore the vehicle. Clear DTCs and retest the system.

  12. 12) Check APP Signal Return Circuit For An Open

    Measure the resistance between PCM body harness connector C1381A terminal No. 33 and APP harness connector terminal No. 9; and PCM connector C1381A terminal No. 20 and APP connector terminal No. 10. See CONTROL MODULE CONNECTOR IDENTIFICATION . Are the resistances less than 5.0 ohms? If yes, install a new PCM. Restore the vehicle. Clear DTCs and retest the system. If no, repair open in signal return circuit. Restore the vehicle. Clear DTCs and retest the system.

  13. 13) DTC P2138, P2139 Or P2140

    Possible causes are:
    • Faulty sensor.
    • Faulty PCM.
    • High circuit resistance.

    Clear all DTCs. Perform the KOEO ON-DEMAND SELF-TEST  under QUICK TEST. Are DTCs P2138, P2139 or P2140 present? If yes, go to next step. If no, if other DTCs are present, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, attempt to recreate fault. Road test the vehicle. Rerun KOEO ON-DEMAND SELF-TEST  under QUICK TEST. If no DTCs are retrieved, restore the vehicle. System is okay.

  14. 14) Check Accelerator Pedal Assembly For Binding

    Depress the accelerator pedal slowly to the floor and release. Does the accelerator pedal move to the floor and back without binding? If yes, go to next step. If no, install a new APP sensor assembly. Restore the vehicle. Clear DTCs and retest the system.

  15. 15) Check APP Sensor Signal Voltage Ranges

    Key on. Access and monitor APP sensor 1, 2, and 3 PIDs. Depress the accelerator pedal slowly to the floor and release. Are the PID voltages within the range specified in APP SENSOR VOLTAGE VALUES  table? If yes, install a new PCM. Restore the vehicle. Clear DTCs and retest the system. If no, install a new APP sensor assembly. Restore the vehicle. Clear DTCs and retest the system.
    APP SENSOR VOLTAGE VALUES

    Pedal Position APP1 APP2 APP3
    Closed Throttle 4.3 Volts 1.2 Volts 0.7 Volt
    Wide Open Throttle 0.8 Volt 4.3 Volts 4.2 Volts
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