OBD-II Code · Computer
P0603
PCM Keep-Alive Memory Error
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$100–$1,500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
KAM memory fault.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Resets adaptive memory
Likely causes
- Weak batteryMost common
- Corroded terminals
- Failed PCM
Read the full diagnostic procedureP0603 indicates the Keep Alive Memory (KAM) section of the PCM has failed its self-test, typically because the constant-power feed to KAM was lost or…
P0603 indicates the Keep Alive Memory (KAM) section of the PCM has failed its self-test, typically because the constant-power feed to KAM was lost or because the memory cells will no longer retain learned data (idle adapts, fuel trims, transmission shift adapts, immobilizer counters).
The cheapest first move is to check the battery
- a fully dead battery, jumpstart event, battery disconnect lasting more than a few minutes, or a corroded battery terminal will all reset KAM and on many platforms set a one-time P0603.
- Clear the code, drive normally to relearn fuel trims and idle, and see if it returns.
- Verify the KAM/B+ fuse (often labeled BATT, ECM-B, or PCM-B in the underhood fuse box) has constant 12V with key off, and check for parasitic draw issues that could be cycling that feed.
- Inspect the battery cable terminations and the PCM main-power circuit for high resistance — anything over 0.1V drop on the B+ feed to the PCM under load is suspect.
- The expensive misdiagnosis is replacing the PCM for a single P0603 that set after a known battery disconnect; on most domestics built after 2005, P0603 will self-clear after a few drive cycles and never return if the underlying power-supply issue is resolved.
Vehicle-specific patterns2004-2010 Ford F-150, Explorer, and Escape commonly set P0603 after a dead battery or jump-start, addressed by simply clearing the code and completin…
- 2004-2010Ford F-150, Explorer, and Escape commonly set P0603 after a dead battery or jump-start, addressed by simply clearing the code and completing the KAM relearn drive cycle per Ford TSB 06-26-3.
- 2003-2007GM trucks with corroded positive battery terminals (the side-post style is especially prone) throw P0603 intermittently until the cable ends are cleaned or replaced.
- 2005-2011Chrysler/Dodge Ram with the TIPM lose KAM power when the internal TIPM B+ relay degrades, setting P0603 along with random no-starts, covered by FCA TSB 08-031-15.
- 2006-2012Honda Accord and Civic set P0603 after aftermarket alarm or stereo installs that briefly disconnect the constant 12V backup to the PCM.
Estimated repair$0 to $1,200.
Look up another code
P0603 — frequently asked
What does a P0603 code mean?
KAM memory fault.
What causes a P0603 code?
Common causes: Weak battery; Corroded terminals; Failed PCM.
What are the symptoms of a P0603 code?
Typical symptoms: Check engine light; Resets adaptive memory.
Is it safe to drive with a P0603 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $100-$1,500.
How do I diagnose a P0603 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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