P0603
PowertrainPcm Memorymoderate severityInternal Control Module Keep Alive Memory (KAM) Error
What P0603 Means
The PCM detected a fault with its Keep Alive Memory, which stores learned values and adaptations. This is usually caused by loss of battery voltage or an internal module fault.
Symptoms
- Check engine light on
- Loss of learned idle/fuel trims
- Rough running after battery disconnect
Common Causes
- Weak or disconnected battery
- Corroded battery/ground connections
- Faulty PCM internal memory
- Poor wiring to constant power circuit
Diagnostic Steps
- Check battery voltage and connections
- Inspect PCM constant power and ground circuits
- Clear code and retest for return
- Reflash or replace PCM if fault persists
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