What has failed with code p0603?

Code P0603 indicates a malfunction in the Engine Control Module (ECM) or Powertrain Control Module (PCM), specifically related to the internal control module memory. This failure can be due to issues such as electrical problems, software corruption, or hardware malfunctions within the module itself. It often results in poor engine performance or drivability issues. To resolve this code, it may require reprogramming or replacing the ECM/PCM.