Idle Shutdown Vehicle Accessories Relay Driver Circuit – Voltage Above Normal, or Shorted to High Source
|Fault Code: 338
Idle Shutdown Vehicle Accessories Relay Driver Circuit – Voltage Above Normal, or Shorted to High Source. 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.
ISX and ISM – Idle Shutdown Vehicle Accessories Relay Driver Circuit
The electronic control module (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 original equipment manufacturer (OEM). The return circuit can be returned to the ECM through the ECM Return (General) or connected directly to ground. Refer to the OEM service literature to determine grounding configuration.
This idle shutdown relay location varies by OEM. Refer to the OEM service literature to determine the location.
Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.
Conditions for Setting the Fault Codes
The idle shutdown relay pulse width modulated (PWM) signal is detected to be at system voltage by the ECM when the PWM voltage is turned off.
Action Taken When the Fault Code is Active
- The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
- The accessories controlled by the idle shutdown relay will be disabled.
Conditions for Clearing the Fault Code
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
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. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.
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 set up incorrectly.
- Open circuit in the idle shutdown relay, OEM harness or connectors.
- Short circuit to a voltage source in the OEM harness or relay.