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PACCAR PX-9 CM2350 (2013-17) Fault Code:1239 PID:SID385 SPN:2623 FMI:3 Accelerator Pedal or Lever Position Sensor 2 Circuit – Voltage Above Normal or Shorted to High Source

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.

The engine will operate in Limp Home mode.

Circuit Description:
The accelerator position sensor is a Hall effect sensor attached to the accelerator pedal. The accelerator position sensor varies the signal voltage to the engine control module (ECM) as the accelerator pedal is depressed and released. Low signal voltage is received by the ECM when the accelerator pedal is at 0 percent. A high signal voltage is received by the ECM when the accelerator pedal is at 100 percent. The accelerator pedal position circuit contains an accelerator pedal position 5 volt supply, accelerator pedal position return, and accelerator pedal position signal.

The accelerator pedal contains two position sensors. These position sensors are used to measure the throttle position. Both position sensors receive a 5 volt supply from the ECM. A corresponding signal voltage based on the position of the accelerator pedal is then received from the ECM. The signal voltage for accelerator position 1 is twice as much as the signal voltage from the accelerator position 2.

Component Location:
The accelerator pedal or lever position sensor is mounted to the accelerator pedal assembly. Refer to the OEM service manual

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the throttle pedal signal voltage was greater than a calibratible value for more than 1 second.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
1) To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
5) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
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 INSITE™ electronic service tool, while flexing the harness to locate the intermittent connection.

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

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Causes:
1) Accelerator pedal position 2 signal circuit shorted to battery or 5-VDC supply
2) Open accelerator pedal return circuit in the harness or connections
3) Accelerator supply shorted to battery
4) Damaged accelerator pedal position sensor