Mercedes Benz

The P0603, P0604, and P0605 trouble codes  indicate different types of internal memory errors within the Powertrain Control Module (PCM), also known as the Engine Control Module (ECM) . Since all three codes point to internal memory faults, they strongly suggest that the PCM itself is defective and needs to be replaced or reprogrammed.   Code definitions P0603—Internal Control Module Keep Alive Memory (KAM) Error:  The PCM's KAM stores learned vehicle settings for optimal performance based on your driving habits. This code sets when the KAM fails its self-test, often caused by a power interruption. P0604—Internal Control Module Random Access Memory (RAM) Error:  The PCM's RAM is its temporary memory, storing information needed for day-to-day operation. This code is logged if the PCM detects a problem with the RAM portion of its memory during a self-check. P0605—Internal Control Module Read Only Memory (ROM) Error:  The PCM's ROM contains the core software and fa...