PACCAR PX-8 CM2150 (2007-09) Fault Code: 1239 PID: SPN: 2623 FMI: 3 Accelerator Pedal or Lever Position Sensor 2 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected at accelerator pedal position number 2 signal circuit.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Newer engines use two throttle position sensors to determine the throttle position. Older throttle pedals used a single throttle position sensor and an idle validation switch. If Fault Codes 132 and 1241 are active when the accelerator pedal is in the idle position and Fault Code 132 goes inactive and Fault Code 1239 goes active when the throttle is depressed, the incorrect throttle pedal has been installed in the vehicle. A throttle pedal with two acceleration position sensors should be installed.

If troubleshooting an intermittent accelerator problem, the accelerator pedal position sensor 2 signal voltage can be monitored with the INSITE™ electronic service tool, while flexing the harness to locate the intermittent connection.

Possible causes:

1)Accelerator pedal position 2 signal circuit shorted to battery or 5 volt supply.
2)Open accelerator pedal return circuit in the harness or connections.
3)Accelerator supply shorted to battery.
4)Failed accelerator pedal position sensor.

Note: The three wires in the accelerator position sensor circuit must be twisted together.

Possible repairs:

1)Replace the accelerator pedal.
2)The removal and installation of the connector may correct the problem.
3)Repair or replace the OEM harness.
4)Replace the ECM.