P0603 code meaning
Internal Control Module Keep Alive Memory (KAM) Error
Powertrain system Generic code P06xx codes Check engine light
What P0603 means
Keep alive memory holds learned values – fuel trim, idle and shift adaptation, readiness status – while the engine is off, as long as the module has constant battery power; CARB defines it as memory that is lost when the battery or fuse is disconnected. The module stores a checksum of this memory at shutdown and compares it at the next start (Ford, GM Europe); GM calls the check 'long term memory reset', and the Ford diesel watches the supply of its engine-off timer chip (below 0.25 V). By far the most common trigger is outside the module: a disconnected, flat or replaced battery or an interrupted constant feed – Nissan bulletins name exactly this and ask for at least 11 V before clearing. Learned values then start from default and the readiness monitors are reset. Whether the lamp comes on depends on the maker.
P0603 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0603
- Check engine light on (depending on the maker)
- Rough idle or changed shifting until values are relearned
- Readiness monitors reset
- Often right after battery work
Common causes of P0603
- Most likelyBattery disconnected, deeply discharged or replaced
- PossibleInterrupted constant power feed to the module (fuse, wire, corrosion)
- Less likelyMain relay drops out too early, memory not saved completely at shutdown
- Less likelyInternal memory defect (EEPROM/NVM)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine control moduleBatteryControl module power supply
What each part of P0603 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 03 | The exact fault in that area. |
What to do next
- Note P0603 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0603
What does P0603 mean?
P0603 means "Internal Control Module Keep Alive Memory (KAM) Error". Keep alive memory holds learned values – fuel trim, idle and shift adaptation, readiness status – while the engine is off, as long as the module has constant battery power; CARB defines it as memory that is lost when the battery or fuse is disconnected. It is a generic code, so it means the same on every make.
Is it safe to drive with P0603?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0603 fail an emissions test?
Yes, it can. P0603 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0603 to fix?
Difficulty: easy. A typical repair takes 0.2 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0603 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.