CID 1234 CAT Fault Code

Cause :

When the ignition switch is turned to ON, voltage from the ECM's MREL terminal is applied to the EFI MAIN relay. This causes the contacts of the EFI MAIN relay to close, which supplies power to terminal +B of the TCM.The Engine and Transmission System is not performing as expected. An issue has been detected in the Engine Electrical System, including the Charging and Starting System that monitors and controls the engine starting system and 12V battery charging system.