Cummins ISB CM850 (2003-06) Fault Code: 431 (NISS) PID: SID 230 SPN: 558 FMI: 2 Accelerator Pedal or Lever Idle Validation Circuit – Data Erratic, Intermittent, or Incorrect. Voltage detected simultaneously on both idle validation and off-idle validation switches.

Possible causes:

1)This fault code is usually caused by an open circuit on either the idle validation on-idle or off-idle signal circuit, a loose connection, uncalibrated accelerator pedal or lever assembly, or miswired idle validation switch.
2)The integrated sensor switch (ISS) has a different internal resistance specification (125 ohms) than the nonintegrated sensor switch (NISS).
3)When installing a new accelerator pedal or lever assembly, it must be calibrated before operating the engine. To calibrate, turn the keyswitch to the ON position and fully depress and release the pedal three times.

Possible repairs:

1)Connect the NISS to the OEM harness
2)Clean the connector and pins.
3)Replace the NISS.
4)Repair or replace the OEM harness.
5)Replace the ECM.