P0603: Internal Control Module Keep Alive Memory (Keep Alive Memory) Error
What to do
Driveable. Expect a rougher idle and possibly odd gear changes for the first fifty miles or so while the module relearns — that part is normal and self-correcting. If it keeps recurring, mention any battery work or a battery that goes flat, because the memory depends on a permanent live feed.
What this code means
The keep-alive memory has failed its check. This is the memory that survives the ignition being switched off — it holds learned fuel trims, idle adaptations, transmission shift adaptations and stored fault history, all of which the module builds up over time to suit the individual engine.
Losing it is not catastrophic but it is noticeable. The engine reverts to base settings and must relearn, so idle may be rough or hunting for the first few dozen miles and an automatic gearbox may shift oddly until its adaptations rebuild.
A very common trigger is simply a battery that has been disconnected or has gone flat, since keep-alive memory depends on a permanent live feed. Where the code returns repeatedly, the permanent supply or its fuse is the thing to check before condemning the module.
Likely causes
Start here
- Battery disconnected or gone flat · easy
- Blown permanent supply fuse · easy
- Corroded battery terminals · easy
Less common
- Degraded module memory · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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