Parts
$5–200
P0603 — Internal Control Module Keep Alive Memory (KAM) Error
CAUTIONIs it safe to drive? ECM long-term memory was corrupted or lost — the engine will relearn most adaptations over a few drive cycles, but get the root cause checked so it doesn't keep happening.
What P0603 means
KAM is the memory that stores learned adaptations — idle trim, fuel trims, transmission shift points, idle relearn values. P0603 means that memory lost its content or failed its integrity check. Often caused by battery issues or power interruptions to the ECM.
Most likely causes (in order)
- Battery discharged or disconnected while ECM was active
- Poor ECM power or ground connection causing intermittent power loss
- Battery itself weak and dropping voltage during heavy loads
- KAM backup capacitor or battery on the ECM board failed (age)
- Fuse for ECM keep-alive circuit blown
Symptoms you might notice
- rough idle after battery disconnection
- transmission shifting oddly until relearned
- poor idle until fuel trims relearn
- CEL on
What to check first
Check the KAM fuse in the underhood fuse box (labeled ECU/ECM BATT or similar) and the main ECM power relay. A blown KAM fuse means the ECM loses memory every key-off cycle — it will continuously set P0603 until the fuse is replaced and the root cause of the blown fuse found.
Repair cost & difficulty
Labor
0.5–2 hr
Difficulty
DIY-friendly