Computer & output circuits · Powertrain · generic (SAE-defined)
P0603: Internal Control Module Keep Alive Memory (KAM) Error
P0603 means the engine computer found that its keep alive memory, which stores learned values such as fuel trims while the key is off, was lost or failed a self-check.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0603 sets
The powertrain control module (PCM) keeps a small memory area powered at all times through a constant battery feed so it can retain adaptive values between drives. If that memory is erased unexpectedly or fails an integrity check at startup, the PCM sets P0603. A dead battery, a blown constant-power fuse or a drain that drops voltage overnight can all trigger it.
Common causes of P0603
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Battery recently disconnected, replaced or fully discharged
- Blown fuse or open in the PCM constant battery feed
- Poor battery terminal or ground connections
- Parasitic drain causing low voltage while parked
- Internal PCM memory fault
P0603 symptoms
- Check engine light on
- Rough or unstable idle after startup until values relearn
- Slightly changed shift feel or fuel economy
- Often no drivability symptoms at all
How P0603 is diagnosed
- Record freeze frame and ask whether the battery was disconnected or went dead recently
- Test the battery and inspect terminals and cables
- Check the PCM constant-power fuse and verify battery voltage at the PCM feed with the key off
- Check for an excessive parasitic draw if the battery keeps running down
- Clear the code, leave the vehicle off overnight and see whether it returns
- If power and grounds are good and the code persists, check for software updates, then consider the PCM
Typical fixes for P0603
- Clear the code after a known battery disconnect and confirm it does not return
- Replace a weak battery or clean and tighten battery connections
- Repair the PCM constant-power fuse or circuit
- Fix a parasitic drain
- Reprogram or replace the PCM if the internal memory has failed
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0603 FAQ
What does code P0603 mean?
P0603 means the engine computer found that its keep alive memory, which stores learned values such as fuel trims while the key is off, was lost or failed a self-check. The standard definition is "Internal Control Module Keep Alive Memory (KAM) Error."
Can I drive with a P0603 code?
Generally yes, for short-term use, if the engine runs normally. Idle and fuel trims may be off until values relearn, and if the code keeps returning the cause should be found within days.
Does disconnecting the battery cause P0603?
On some vehicles it can, because the stored learned values are wiped. If the code clears and stays away after the vehicle relearns, no repair is usually needed.
Why does my car idle poorly after this code?
The PCM has lost learned idle and fuel values and is starting from defaults. Idle usually smooths out after several drive cycles once the values are relearned.
Keep researching
More computer & output circuits codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.