CID 691 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.This combination is associated with interruptions in the ignition cylinders of the power unit. The cylinder number is not indicated, therefore, the user must independently check each element, including compression.