Cummins ISB4.5 CM2150 Fault Code: 338 PID: SID 87 SPN: 1267 FMI: 3 Idle Shutdown Vehicle Accessories Relay Driver Circuit – Voltage Above Normal, or Shorted to High Source.

Circuit Description
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 manual to determine grounding configuration.

Component Location
This idle shutdown relay location varies by OEM. Refer to the OEM service manual 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
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

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.

Possible Causes
-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.