Cummins ISX15 CM2250 (2010-12) Fault Code: 1242 PID: 91 SPN: 91 FMI: 2 Accelerator Pedal or Lever Position Sensor 1 and 2- Data Erratic, Intermittent, or Incorrect

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 electronic 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 for accelerator position 2.

Component Location
The accelerator pedal position sensor is located on the accelerator pedal. Refer to the OEM service manual.

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

Conditions for Setting the Fault Codes
The ECM detects that the readings between accelerator position sensor 1 and accelerator position sensor 2 differ by more than 2 percent.

Action Taken When the Fault Code is Active
The ECM illuminates the red STOP ENGINE light immediately when the diagnostic runs and fails.
Conditions for Clearing the Fault Code
To validate the repair, start the engine and let it idle for 1 minute.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the red STOP ENGINE lamp after the diagnostic runs and passes.
For OBD engines, the ECM will turn off the Malfunction Indicator Lamp (MIL) after 3 consecutive trips where the diagnostic runs and passes.
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.This fault code becomes active when the accelerator position sensor number 1 and accelerator position sensor number 2 are not reading the same value.Possible causes of the fault include:

Damaged accelerator pedal position sensor number 1 or damaged accelerator pedal position sensor number 2
Accelerator pedal position sensor number 1 and accelerator pedal position sensor number 2 signal wires are shorted together.
Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:
1) Low Sensor supply Voltage
2) OEM harness
3) ECM calibration