DTC P0603: ECM/PCM Internal Circuit Malfunction (Keep Alive Memory (KAM) Error)

Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Wait 1 second.
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM (see ECM/PCM UPDATING AND SUBSTITUTION FOR TESTING ), then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
2. NO - Intermittent failure, system is OK at this time.