P0603 Code: Internal Control Module Keep Alive Memory (KAM) Error
Your engine computer doesn't just react in real time — it also stores "learned" values (like idle and fuel trim adjustments) in Keep Alive Memory (KAM) so it doesn't have to relearn them every time you start the car. P0603 sets when that memory fails.
What P0603 Means
Keep Alive Memory (KAM) is a section of the module's memory that stays powered by a constant battery feed, even with the ignition off, so learned adaptive values persist between drives. P0603 indicates the module has detected a fault in this specific memory, distinct from the general checksum error covered by P0601.
Common Causes
- Loss of constant power to the module (a blown fuse, damaged wiring, or a poor connection on the KAM circuit)
- A weak or disconnected battery causing repeated KAM resets, which can sometimes trigger this code over time
- An internal memory hardware fault within the module itself
Common Symptoms Alongside P0603
- Rough idle or stalling shortly after starting, since learned idle values were lost
- Temporary poor fuel economy or hesitation as the module relearns adaptive values
- Check Engine Light on, sometimes intermittently
What to Check Before Assuming Module Failure
Because this code is closely tied to constant power supply, it's worth checking the relevant fuse and constant-power wiring to the module before assuming the module's internal memory hardware has failed. A battery that's been disconnected or gone dead recently can also trigger a KAM-related code temporarily — if the code doesn't return after a normal drive cycle, it may not indicate a hardware fault.
When Replacement Is the Right Call
If constant power and grounds check out fine and the code returns repeatedly, the module's internal KAM circuitry itself is the likely cause, and replacement with a properly matched unit is the appropriate next step.
Frequently Asked Questions
Will disconnecting my battery cause this code?
It can trigger a temporary KAM-related code as the module relearns values, but this typically clears after a normal drive cycle rather than returning repeatedly.
Is a blown fuse a common cause of P0603?
Yes — checking the fuse and wiring on the module's constant power circuit is one of the first things worth ruling out.
Does P0603 always mean the module needs replacing?
Not always — only if a power/ground/fuse check doesn't resolve it and the code returns.
If you've ruled out a power supply issue and P0603 persists, browse tested, OEM-quality replacement ECMs, PCMs & ECUs, or contact our team with your VIN.