CID 398 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.Associated with low engine fluid pressure. The reason most likely is the lack of oil in the engine, so first of all you need to check the amount of consumable. You should also make sure that the engine fluid pressure sensor is working.