CM850 Electronic Control System – 019-086   Accelerator Pedal or Lever Position Sensor Circuit

CAUTION  Do not use probes or leads other than Part Number 3822758. The OEM connector will be damaged. The leads must fit tightly in the connector without expanding the pins in the connector.

If INSITE™ electronic service tool is available, monitor the accelerator position sensor circuit for proper operation. If not, follow the troubleshooting procedures in this section.

Disconnect the OEM harness connector from the ECM. Make sure the sensor is connected to the OEM harness. Insert a test lead into the accelerator pedal/lever position +5 volt supply pin of the OEM harness connector and connect it to the multimeter probe. Insert the other lead into the accelerator pedal/lever position return of the connector and connect it to the other multimeter probe.

With the accelerator pedal depressed, measure the resistance. The multimeter must show 2000 to 3000 ohms when the accelerator pedal is down. If the resistance is not within the specification, there is a problem with the accelerator pedal/lever position +5 volt supply wire or the accelerator pedal/lever position return wire in the OEM harness, provided the accelerator position sensor has been previously checked. Repair the OEM harness according to the manufacturer’s procedures.

Repeat the check with the accelerator pedal in the released position. Measure the resistance. The multimeter must show 2000 to 3000 ohms when the accelerator pedal is up. If the resistance is not
within the specification, there is a problem with the accelerator pedal/lever position +5 volt supply wire or the accelerator position pedal/lever return wire in the OEM harness, provided the accelerator position sensor has been previously checked. Repair the OEM harness according to the manufacturer’s procedures.

Remove the test lead from the accelerator pedal/lever position return pin and insert it into the accelerator pedal/lever position signal pin.

Make sure the foot pedal is in the released (idle) position.

Measure the resistance. The multimeter must show 1500 to 3000 ohms.

Depress the accelerator pedal assembly (full-fuel) and measure the resistance again.

The multimeter must show 200 to 1500 ohms. This resistance value must be at least 1000 ohms lower than the resistance value of 1500 to 3000 ohms measured in the above check. If the resistance values are not within the specification, there is a problem with the accelerator pedal/lever position +5 volt supply or the accelerator position pedal/lever signal wire in the OEM harness.

Repair the OEM harness according to the manufacturer’s procedures.

If the resistance values in the two previous checks are within the specification, the accelerator pedal/lever position +5 volt supply, the accelerator pedal/lever position return, and the accelerator pedal/lever position signal wire must still be checked for a short circuit to ground, a short circuit from pin to pin, and a short circuit to battery supply.

NOTE: When checking the OEM harness, inspect the bulkhead connector and other connectors in the circuit for corrosion or damage to the accelerator position sensor wire terminals.

Disconnect the accelerator pedal/lever position sensor and assembly from the OEM harness at the accelerator pedal/lever position sensor and assembly.

Insert a test lead into the accelerator pedal/lever position +5 volt supply pin of the OEM harness connector and connect it to the multimeter positive probe. Touch the multimeter negative probe to the engine block ground and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

Remove the lead from the accelerator pedal/lever position +5 volt supply pin and insert it into the accelerator pedal/lever position return pin of the OEM harness connector. Touch the multimeter negative probe to the engine block ground and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

Remove the lead from the accelerator pedal/lever position return and insert it into the accelerator pedal/lever position signal pin. Touch the multimeter negative probe to the engine block ground and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

If any of these three resistance measurements are not open, there is a short circuit to ground between the wires connected to the accelerator pedal/lever position +5 volt supply, the accelerator pedal/lever position return, or the accelerator pedal/lever position signal wire. Repair the OEM harness. Refer to the OEM troubleshooting and repair manual for the procedures.

Disconnect the accelerator pedal/lever position sensor and assembly from the OEM harness at the accelerator pedal/lever position sensor and assembly.

Insert the test lead into the accelerator pedal/lever position +5 volt supply pin of the OEM harness connector. Insert the other lead into the idle validation on-idle signal pin of the accelerator pedal assembly connector. Connect the clips to the multimeter probes and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

Remove the lead from the idle validation on-idle signal pin and test all other pins in the OEM harness connector, one at a time.

The multimeter must show an open circuit (100k ohms or more) at all pins.

If the multimeter did not indicate an open circuit at every pin, there is a short circuit between the accelerator pedal/lever position
+5 volt supply wire and any other wire that did not measure an open circuit. Repair or replace the OEM harness. Refer to Procedure 019-071 for harness replacement.

Remove the lead from the accelerator pedal/lever position +5 volt supply pin and insert it into the accelerator pedal/lever position return pin. Insert the other lead into the idle validation on-idle signal pin in the OEM harness connector and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

Remove the lead from idle validation idle signal pin and test all other pins in the OEM harness connector, one at a time.

The multimeter must show an open circuit (100k ohms or more) at all pins.

Remove the lead from the accelerator pedal/lever position return pin and insert it into the accelerator pedal/lever position signal pin. Insert the other lead into the first pin in the OEM harness connector and measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

Remove the lead from the first pin in the OEM harness connector and test all other pins in the connector, one at a time.

The multimeter must show an open circuit (100k ohms or more) in all pins.

If the multimeter did not indicate an open circuit on every pin, there is a short circuit between the accelerator pedal/lever position signal wire and any other wire that did not indicate an open circuit. Repair the OEM harness according to the vehicle manufacturer’s procedures.

Disconnect the accelerator pedal/lever position sensor assembly from the OEM harness at the accelerator pedal/lever position sensor assembly.

Turn the keyswitch to the ON position. Adjust the multimeter to measure VDC.

Insert a test lead into the accelerator pedal/lever position return pin. Touch the multimeter negative probe to the engine block ground and measure the voltage.

The voltage must be 1.5 VDC or less.

Remove the lead from the accelerator pedal/lever position return pin and insert it into the accelerator pedal/lever position signal pin. Touch the multimeter negative probe to the engine block and measure the voltage.

The voltage must be 1.5 VDC or less.

If more than 1.5 VDC is measured at any pin, there is a short circuit from the accelerator pedal/lever position +5 volt supply, the accelerator pedal/lever position return, or the accelerator pedal/lever position signal to a wire carrying power in the OEM harness.

NOTE: An external voltage source is any wire in the OEM harness that carries voltage.

Replace the OEM harness. Refer to Procedure 019-071. Connect all components after completing the repair.