P0603 Code: Internal Control Module Keep Alive Memory (KAM) Error
🟠 Moderate severity · drivable
Drivable, but the PCM has lost its stored settings, which usually points to a battery or PCM problem.
What P0603 means
The engine control module's keep-alive memory (which stores learned settings like idle and fuel trims) has been lost or corrupted. This often happens after a battery disconnect or from a failing battery/PCM.
Symptoms
- Check engine light is on
- Rough running after battery disconnect
- Lost radio or memory settings
- Poor fuel economy until it relearns
Common causes
- most common: Battery disconnected or weak
- common: Low battery voltage
- less common: Faulty engine control module
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Test the battery and charging system, replace if needed | Yes | $100–250 |
| Reprogram or replace the engine control module | Mechanic | $300–1500 |
Frequently asked questions
Can I drive with a P0603 code?
Yes. The engine will often relearn its settings over a few drive cycles, but check the battery and charging system.
What is the most common cause of P0603?
A battery disconnect or weak battery that let the PCM lose its keep-alive memory.
How much does it cost to fix a P0603?
Often just a battery ($100–$250). A PCM replacement is $500–$1,500 if the module itself is faulty.
Related codes
P0601
P0601 Code: Internal Control Module Memory Check Sum Error
P0602P0602 Code: Control Module Programming Error
P0606P0606 Code: ECM/PCM Processor Fault
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.