P0603 Fault Code in Land Rover: Causes, Symptoms, and Fixes

The vehicle’s ECU/TCM/PCM (Engine or Transmission Control Module) has a Keep Alive Memory (KAM), which stores adaptive values and learned data (like fuel trims, transmission shift points, idle speed, etc.). This code appears when the module detects a loss of stored memory or when the KAM self-check fails.

Common Causes:

1. Battery disconnected recently
2. Weak or failing battery
3. Faulty or loose battery terminals/ground connections
4. ECU/PCM/TCM internal fault
5. Issues with the power supply circuit to the control module

Symptoms:

1. Check Engine Light (CEL) on
2. Hard starting or stalling after startup
3. Poor idle or drivability issues until ECU relearns values
4. Transmission may shift harshly until adaptive data is relearned

Fixes:

1. Check battery condition – Ensure battery is healthy and fully charged.
2. Inspect battery terminals & grounds – Clean and tighten connections.
3. Check for recent battery disconnection – Code may clear after a few drive cycles.
4. Check fuses and power supply to ECU/TCM.
5. If everything else is fine, ECU/PCM/TCM may be faulty and need reprogramming or replacement.