Fault-Code Library · Engine electronics
P0603: Internal control module keep-alive memory error
The engine controller has lost or detected corruption in memory retained when the ignition is off.
Common symptoms
- •Engine warning light
- •Lost adaptations
- •Hard starting
- •Multiple unrelated codes
Likely causes
- •Weak or disconnected battery
- •Poor ECU power supply
- •Aftermarket wiring
- •Internal controller fault
First checks
- •Test battery and charging health
- •Inspect constant ECU power and grounds
- •Review recent battery or programming work
Important
Prove stable voltage and power supply before replacing or programming an expensive engine controller.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
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