P0603
Internal Control Module Keep Alive Memory (KAM) Error
Engine control module (ECM)
Generic OBD-II
High
What it means
P0603 means the engine control module found a fault in its keep-alive memory — the small amount of storage kept powered with the key off so the ECM remembers learned fuel trims and idle settings. It's often triggered by a weak battery, a bad ground, or losing constant power, and until those learned values are restored the engine can idle rough, start hard, or stall.
High
Can I keep driving? Be cautious — the ECM has lost its learned settings, which can cause rough running, hard starting, or a no-start, so get it diagnosed promptly.
Common symptoms
What you'll notice
- Check-engine light on
- Rough or unstable idle and poor drivability after startup
- Hard starting or intermittent no-start
- Other monitors won't complete / readiness not set
Common causes
Most likely first
- Weak, dead, or recently disconnected battery (KAM loses its keep-alive power)Likely
- Corroded or loose battery terminals or ground connectionsCommon
- Charging-system problem or voltage drop on the KAM power feedCommon
- Wiring fault in the constant-power (memory) circuit to the moduleLess often
- Internal ECM faultLess often
How to diagnose & fix
Work through it in order
- Load-test the battery and inspect/clean the battery terminals and main grounds first.
- Check the charging-system voltage and the ECM's constant-power (KAM) fuse and feed.
- Verify the memory circuit holds voltage with the key off.
- Clear the code, let the ECM relearn idle/fuel trims over a few drive cycles, and re-check.
- If the code returns with good power and grounds, the ECM likely needs reprogramming or replacement.
FAQ
Quick answers
Is it safe to drive with P0603?+
Drive cautiously. The ECM has lost its learned adjustments, so idle and starting may be rough and it can stall until power/ground faults are fixed and it relearns.
Can I just clear P0603?+
You can, and it may clear if triggered by a one-time battery disconnect — but if the battery, grounds, or memory circuit are faulty it will return.
Related codes
Often seen with P0603
Read & clear P0603 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX