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. There is one 30-ampere fuse in the unswitched battery wires to protect the original equipment manufacturer (OEM) harness. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON. The battery return wires are connected directly to the negative (-) battery post.

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 ECM detects that the main battery supply voltage is greater than +36-VDC.

Action Taken When the Fault Code is ActiveThe ECM logs the fault code and illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.Conditions for Clearing the Fault CodeTo validate the repair, perform a key cycle, and leave the key in the ON position for 1 minute.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the battery voltage is below +36-VDC and the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp 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 TalkThis fault code is logged when the ECM battery supply voltage exceeds +36-VDC. Causes of this fault code include:

Faulty alternator or regulator that is overcharging the systemBatteries connected in series instead of parallelIncorrect jump-starting procedure.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:1) Battery System2) Alternator failure3) ECM calibration