CM870 and ISX Engines – FAULT CODE 338

Idle Shutdown Vehicle Accessories Relay Circuit


Fault Code: 338
PID: S087
SPN: 1267
FMI: 3/3
LAMP: Amber

Idle Shutdown Vehicle Accessories Relay Circuit – shorted high. Open circuit or short to voltage source detected at the idle shutdown vehicle accessory/ignition bus relay circuit.

Vehicle accessories or ignition bus loads controlled by the idle shutdown relay will not power up.

Idle Shutdown Vehicle Accessories Relay Circuit

Circuit Description

The ECM idle shutdown feature has an optional parameter for a shutdown accessory relay. When this parameter is set to “Installed”, the ECM sends a signal to energize the relay and turn off vehicle accessories during idle shutdown events. The idle shutdown relay return circuit varies by OEM. The return circuit may be returned to the ECM through pin 42 or connected directly to ground. Refer to the OEM service literature to determine grounding configuration.

Component Location

The idle shutdown relay location varies by OEM. Refer to the appropriate OEM service literature to determine the location.

Shop Talk

The ECM monitors the voltage level on this circuit. If it detects a voltage when the signal is commanded OFF, it records this fault code. This fault code can be caused by:

  • ECM idle shutdown feature setup incorrectly
  • Open circuit in the idle shutdown relay, OEM harness or connectors
  • Short circuit to a voltage source in the OEM harness or relay.

Refer to Troubleshooting Fault Code t05-338

Last Modified:  01-Sep-2010