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Home >> Ford >> 2003 >> Excursion 5.4 L, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System Test A Through DU - CNG, Flex-Fuel & Gasoline >> Test DK: Electronic Throttle Control & Accelerator Pedal Position Sensor >> Testing
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Test DK: Electronic Throttle Control & Accelerator Pedal Position Sensor: Testing

  1. 1) For KOEO, KOER & Continuous Memory DTCs P2121-P2123, P2126-P2128 & P2131-P2133: Check Accelerator Pedal Assembly For Binding

    These DTCs indicate that one of the Accelerator Pedal Position sensor fault flags is set for sensor by the PCM, indicating that signal is out of the normal self-test operating range. Possible causes are:
    • APP sensor defective.
    • APP sensor is open, or shorted to ground or power.
    • APP sensor assembly is binding.
    • APP sensor signal circuits shorted together.
    • Damaged PCM.

    The following steps should be taken in order due to the nature of the Electronic Throttle Control system:

    1. These DTCs effect system operation and must be repaired first: P0102, P0103, P0122, P0123, P0222, P0223, P0320, P0715, P0720, P0500 and P2135. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
    2. These DTCs must be repaired next due to the nature of the system: P2121, P2122, P2123, P2126, P2127, P2128, P2131, P2132 and P2133. Go to next step.
    3. If DTCs P2111 or P2112 are present, go to TEST DV step 1) .
    4. If DTC U0300 is present, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

    Turn ignition switch to ON position. Depress accelerator pedal slowly to the floor and release. Does the accelerator pedal move to the floor and back without sticking? If yes, go to next step. If no, isolate and repair binding, or replace pedal/sensor assembly.

  2. 2) Check APP Sensor Signal Voltage Ranges

    Turn ignition switch to ON position. Access and monitor APP sensor 1, 2, and 3 PIDS. Depress accelerator pedal slowly to the floor and release. Are the open and closed voltages within the specified table ranges? See APPS SIGNAL VOLTAGES  table. If yes, go to step  9). If no, for DTCs P2121 and P2122 alone, DTCs P2126 and P2127 alone, or DTCs P2131 and P2132, go to step  4). For any combination of these groups, go to next step.
    APPS SIGNAL VOLTAGES

    Pedal Position APP1 APP2 APP3
    Closed Throttle 4.0-4.2 V 1.4-1.6 V 0.8-1.0 V
    Wide Open Throttle 0.8-1.0 V 3.8-4.0 V 3.2-3.4 V

  3. 3) Check For VREF Voltage At The APP Sensor Harness Connector

    Turn ignition switch to OFF position. Disconnect APP sensor harness connector. Turn ignition switch to ON position. Measure voltage between ETC REF and ETC RTN circuits, and then between ETC REF and SIG RTN circuits at the APP sensor harness connector. See Figure. Measure voltage between the other ETC REF and ETC RTN, and then between the other ETC REF and SIG RTN at the APP sensor harness connector. Are both voltages between 4 and 6 volts? If yes, go to next step. If no, go to TEST C, step  1).
    4. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  4. 4) Check The APP Sensor Circuits For Open In Harness
    Accelerator Pedal Position sensor fault flag is set for sensor by the PCM, indicating that signal is out of the normal self-test operating range. Possible causes of DTCs are:
    • APP sensor defective.
    • APP sensor is open, or shorted to ground or power.
    • APP sensor signal circuits shorted together.
    • Damaged PCM.

    For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 circuit, and for DTCs P2131 and P2132, check only the APP3 circuit. Turn ignition switch to OFF position. Disconnect PCM harness connector. Measure resistance of the APP2 and APP3 circuit, between the APP sensor connector and PCM harness connectors. Are the resistances less than 5 ohms? If yes, for DTCs P2123, P2128 and P2133, go to next step. For DCTs P2121, P2122, P2126, P2127, P2131 and P2132, go to step  7). If no, isolate and repair open circuit.

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

  5. 5) Check APP Sensor Harness For Signal Short To The ETCREFS In Harness
    Accelerator Pedal Position sensor is out of range high. Possible causes of DTCs are:
    • APP sensor is defective.
    • APP sensor assembly is binding.
    • APP sensor harness is shorted to power.
    • Damaged PCM.

    For DTCs P2121 and P2123, check APP1 circuit only, for DTCs P2126 and P2128 check APP2 circuit only, and for DTCs P2131 and P2133 check APP3 circuit only. Disconnect PCM and APP sensor harness connectors. Measure resistances between the APP1, APP2 and APP3, and the ETC REF at the APPS harness connector. Measure resistances between the APP1, APP2 and APP3, and the other ETC REF at the APPS harness connector. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair short circuit.

  6. 6) Check The APP Sensor Circuits For Short To PWR

    For DTCs P2121 and P2123, check APP1 circuit only, for DTCs P2126 and P2128, check APP2 circuit only, and for DTCs P2131 and P2133 check APP3 circuit only. Disconnect PCM and APP sensor harness connectors. Turn ignition switch to OFF position. Measure resistance between the APP1, APP2 and APP3, and battery power at the APP sensor harness connector. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair short circuit.

  7. 7) Check APP Sensor Circuits For Short To SIG RTN & ETC RTN

    For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 circuit, and for DTCs P2131 and P2132, check only the APP3 circuit. Disconnect PCM and APP sensor harness connectors. Measure resistance between APP1, APP2 and APP3 circuits, and SIG RTN circuit at the APP sensor harness connector. Measure resistance between APP1, APP2 and APP3 circuits, and ETC RTN circuit at the APPS sensor harness connector. Are the resistances greater than 10 k/ohms? If yes, for DTCs P2121, P2122, P2126, P2127, P2131 and P2132, go to next step. For all others, go to step  9). If no, isolate and repair short circuit.

  8. 8) Check The APP Sensor Circuits For Short To GND

    For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 circuit, and for DTCs P2131 and P2132 check only the APP3 circuit. Turn ignition switch to OFF position. Measure resistance between the APP1, APP2 and APP3 circuits at APP harness connector and battery ground. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair short circuit.

  9. 9) Check APP Sensor Signals For Short To Each Other In Harness

    For DTCs P2104, P2121, P2126 and P2131, perform only APP1 to APP2 check, and APP1 to APP3 check, and for DTC P2104, perform only APP2 to APP3 check. Disconnect PCM and APP sensor harness connectors. Measure resistances between the APP1 and APP2 circuits at the APP sensor harness connector. Measure resistances between the APP1 and APP3 circuits at the APP sensor harness connector. Measure resistances between the APP2 and APP3 circuits at the APP sensor harness connector. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair short circuit.

  10. 10) Check APP Sensor For Proper Resistance Through Sensor

    Disconnect PCM and APP sensor harness connectors. Measure resistances between ETC REF and ETC RTN circuits through the APP sensor, with the accelerator pedal in the "up" position. Measure resistances between the APP1 and ETC RTN circuits though the APP sensor. Measure resistances between the APP2 and ETC RTN circuits though the APP sensor. Measure resistances between the APP3 and ETC RTN circuits though the APP sensor. Are the resistances within the table ranges? See APP SENSOR CIRCUIT RESISTANCES  table. If yes, go to next step. If no, replace APP sensor. If DTC returns, go to appropriate test step and repair. If fault repairs do not fix symptom or DTC, go to next step.
    APP SENSOR CIRCUIT RESISTANCES

    Circuit Closed Throttle Resistance (Ohms)
    ETC REF To ETC RTN 1400-1500
    APP1 To ETC RTN 4600-5000
    APP2 To ETC RTN 2600-3000
    APP3 To ETC RTN 2200-2600

  11. 11) Check APP Sensor For Voltage Spikes During Operation

    Connect PCM and APP sensor harness connectors. Turn ignition switch to ON position. Access and monitor APP1, APP2 and APP3 PIDs. Depress accelerator pedal slowly and release. Do the PID'S display a smooth voltage reading during the entire pedal travel (no voltage spikes)? If yes, go to next step. If no, replace APP sensor.

  12. 12) Check APP Sensor For Intermittent Signal

    Start engine and bring to idle. Run throttle up to 1500 RPM for 5 seconds. Access APP1 PID, and monitor for a fault indication while completing the following: Lightly tap on he APP sensor, and wiggle the harness connector to simulate road shock (repeat procedure for APP2 and APP3 PIDs). Are any of the PID voltages below the minimum (.7 V), or above the maximum (4.6 V)? If yes, inspect APP sensor harness connector. If connector is okay, replace APP sensor. If no, go to next step.

  13. 13) Check APP Sensor Harness For Intermittent Opens Or Shorts

    Turn ignition switch to ON position, with engine off. Access APP1 PID, and monitor for a fault indication while completing the following: Grasp the vehicle harness closest to the APP sensor connector. Shake and bend a small section of the harness all the way from the dash panel to the PCM (repeat procedure for APP2 and APP3 PIDs). Are any of the PID voltages below the minimum (.7 V), or above the maximum (4.6 V)? If yes, isolate and repair as necessary. If no, unable to identify fault. Go to TEST Z, step 1) . If TEST Z does not identify fault, replace PCM.
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