Trouble code
P0603
Internal Control Module Keep Alive Memory Error
What P0603 means
The engine computer lost its retained memory, usually because power to it was interrupted.
Symptoms you may notice
- Check engine light
- Rough running until the computer relearns
- Idle relearn needed
Common causes, cheapest first
- Battery disconnected or gone flat
- Corroded battery terminals
- Failing battery
- Faulty computer in rare cases
Before you buy anythingThis very often follows a battery change or a flat battery. Sort the battery and connections, clear the code, and let the vehicle relearn its idle before assuming the computer has failed.
What to do next
- Confirm the code with your own scan tool, or have it read free at a chain parts store.
- Decode your VIN so you know your exact engine and build date.
- Work down the causes above from cheapest to most expensive.
- Search NHTSA for a recall or service bulletin covering this symptom on your vehicle.
- Read the batteries buying guide before ordering.
P0603 is a generic OBD-II code, standardized across every make and model sold in the US from 1996 onward. The meaning is the same on any vehicle; the specific part and its location are not.
Parts
Parts commonly needed for P0603
These go to Amazon. We earn a commission if you buy, at no extra cost to you — see our affiliate disclosure. Which one you actually need depends on diagnosis — read the note above first.
Confirm fitment against your VIN on the listing page before ordering. A part that matches your year and model can still be wrong for your build date or engine code.