Circuit DescriptionThe electronic 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 vehicle keyswitch wire when the vehicle keyswitch is turned ON.

Component LocationThe ECM is connected to the battery by the OEM power harness through the ECM battery supply stub. This 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.

Conditions for Setting the Fault CodesThe ECM detects that primary ECM power supply dropped below a calibratible value while the keyswitch was in the ON position. The fault code will be active when the keyswitch is turned on following the incomplete power-down event.

Action Taken When the Fault Code is ActiveThe ECM records 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 shut it down properly. The ECM must see adequate primary ECM battery voltage when the keyswitch is turned OFF before the fault code will go inactive.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.

Shop TalkPossible causes of this fault code are:

Battery voltage below 6.2 VDC during crankingHigh resistance in the ECM supply or return circuitUse 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 Connection/ Terminals2) Battery Failure3) Fuses4) OEM power Harness5) ECM power harness6) OEM harness7) ECM calibration