Electronic Control System Signature, ISX and QSX15 Engines – 019-086   Accelerator Pedal or Lever Position Sensor Circuit

CAUTION  Do not use probes or leads other than Part No. 3822758. The OEM connector will be damaged. The leads must fit tightly in the connector without expanding the pins in the connector.

If INSITE™ 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 pin 48 (accelerator position (+) 5-VDC supply) of the OEM harness connector and connect it to the multimeter probe. Insert the other lead into pin 49 (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 (or up). If the resistance is

not within the specification, there is a problem with wire 48 or wire 49 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 (or down). If the resistance is

not within the specification, there is a problem with wire 48 or wire 49 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 pin 49 (accelerator position return) and insert it into pin 47 (accelerator position signal).

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

Measure the resistance. The multimeter

must show 1500 to 3000 ohms.

Depress the foot pedal (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 wire 48 (accelerator position (+) 5-VDC supply) or wire 47 (accelerator position signal) 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, wire 48, 49, and 47

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 APS wire terminals.

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

Insert a test lead into pin 48 (accelerator position (+) 5-VDC supply)
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 pin 48 (accelerator position (+) 5-VDC supply)
and insert it into pin 49 (accelerator position return) 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 pin 49 (accelerator position return)
and insert it into pin 47 (accelerator position signal). 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 pins 48, 49, or 47. Repair the OEM harness. Refer to the OEM troubleshooting and repair manual for the procedures.

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

Insert the test lead into pin 48 (accelerator position (+) 5-VDC supply)
of the OEM harness connector. Insert the other lead into pin 6 of the 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 pin 6 and test all other pins in the connector, one at a time.

The multimeter

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

If the multimeter shows a closed circuit at any pin, there is a short circuit between wire 48 and any other wire that measured a closed circuit. Repair or replace the OEM harness. Refer to Procedure

019-250 for harness repair or Procedure

019-071 for harness replacement.

Remove the lead from pin 48 and insert it into pin 49 (accelerator position return). Insert the other lead into pin 6 and measure the resistance.

The multimeter

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

Remove the lead from pin 6 and test all other pins in the connector, one at a time.

The multimeter

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

Remove the lead from pin 49 and insert it into pin 47 (accelerator position signal). Insert the other lead into pin 1 and measure the resistance.

The multimeter

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

Remove the lead from pin 1 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 shows a closed circuit at any pin, there is a short circuit between wire 47 and any other wire that measured a closed circuit. Repair the OEM harness according to the vehicle manufacturer’s procedures.

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

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

Insert a test lead into pin 48 (accelerator position (+) 5 VDC supply)
of the OEM harness connector. Connect the lead to the multimeter positive probe. 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 pin 48 and insert it into pin 49 (accelerator position return). 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 pin 49 and insert it into pin 47 (accelerator position signal). 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 wire 48, 49, or 47 to a wire carrying power in the OEM harness.

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

Repair the OEM harness. Refer to Procedure

019-250. Connect all components after completing the repair.