Circuit DescriptionThe engine control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. The ECM receives switched battery input through the keyswitch wire when the keyswitch is turned ON.

Component LocationThe ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the original equipment manufacturer (OEM). Refer to the OEM service manual.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the primary ECM power supply dropped below a calibratible value while the keyswitch was in the ON position.The power down sequence was interrupted by a premature ECM shutdown.Action Taken When the Fault Code is ActiveThe ECM logs the fault code immediately when the diagnostic runs and fails.Power-down data like trip information, maintenance monitor, and fault information will not get saved to permanent memory when the keyswitch is turned OFF.Conditions for Clearing the Fault CodeTo validate the repair, start the engine, let it idle for 1 minute, and then shutdown the engine.Turn the key switch OFF and allow the ECM to completely powerdown.The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after 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 TalkPossible causes of this fault code are:

Battery voltage below 6.2 VDC during cranking.High resistance in the ECM supply or return circuit.Use of a battery disconnect switch or any device that disconnects battery voltage to the ECM to turn the engine off or before the ECM is completely powered down.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Cause:1) Loose Connections/ Terminals2) Battery Failure3) Fuses4) OEM power harness failure5) ECM power harness failure6) OEM harness7) ECM calibration