P0603 Internal control module keep alive memory (KAM) error
What P0603 means
The engine control unit keeps learned values such as fuel trims and idle settings in memory that needs constant battery power. That memory was lost or found invalid, which happens after power interruptions but can also mean a supply or control unit fault.
P0603 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- High
- Typical repair cost
- 80–800 €
- Workshop time
- 0.1–4 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- No
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Rough idle or poor running until values are relearned
- Stalling
- Code returning after every battery disconnect or start
Common causes
- Battery recently disconnected or run flat
- Loose or corroded battery terminals
- Blown fuse for the ECU permanent power supply
- Poor ECU ground
- Internal engine control unit fault
Can I keep driving with P0603?
Have it checked within a day or two. If it appeared right after battery work and does not return once cleared, it was likely harmless; if it keeps returning, the engine may run worse over time.
What to check first
- Check whether the battery was recently disconnected, then clear the code and see if it returns
- Check battery condition and terminals
- Check the ECU permanent power fuse and ground connections
- Have the control unit tested or replaced if supply is good and the code returns
Related codes
- P0602 Control module programming error
- P0604 Internal control module random access memory (RAM) error
- P0601 Internal control module memory checksum error
- P0605 Internal control module read only memory (ROM) error
- P0600 Serial communication link
- P0606 Control module processor fault
- P0607 Control module performance
- P0610 Control module vehicle options error
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
Updated: