Electrical and sensors

P0603 — Control Module Keep Alive Memory (KAM) Error

Severity: medium Safe to drive

What P0603 means

The engine control module stores learned values in Keep Alive Memory (KAM), such as fuel trim and idle adaptations. This memory stays powered even with the ignition off. P0603 sets when the module's self-test finds an error in this memory or its supply, and the stored data may be lost.

Symptoms

  • Check Engine light on
  • Unstable idle after adaptations reset
  • Harsh shifts or lost transmission adaptations
  • Previously stored codes and readiness data erased
  • Hard starting in some cases
  • Symptoms depend on which internal function is affected

Possible causes

  1. Voltage drop or battery disconnect during programming or operation
  2. Weak or worn battery, poor terminals
  3. Poor power or ground to the module: corrosion or a wiring break
  4. Charging system fault or voltage spikes
  5. Outdated or failed software update
  6. Internal module failure

How to diagnose

  1. Read all codes and freeze frame data, record them, then clear codes
  2. Test the battery: resting voltage, cranking voltage, terminal condition and tightness
  3. Measure charging voltage with the engine running and confirm it is stable
  4. Check the module's fuses, relays, constant power feed and grounds
  5. Inspect the module connector and harness for corrosion, moisture or past repairs
  6. Check software version and look for manufacturer bulletins or updates
  7. Clear the code and see if it returns after several drive cycles

Common fixes

  • Charge or replace the battery, clean and tighten terminals
  • Repair power and ground circuits or damaged wiring to the module
  • Fix the alternator or voltage regulator
  • Update or reflash the module software
  • Replace or repair the module if the code returns with good power supply

Questions and answers

What does P0603 mean?

The engine control module found an error in its keep alive memory, where learned adaptations are stored. The cause is most often power supply to the module, and less often the module itself.

Can I drive with P0603?

Usually yes, but the engine and transmission may feel rough while they relearn. If the engine stalls or runs badly, have it diagnosed soon.

Do I need a new ECM for P0603?

Not right away. Check the battery, charging system, module power and grounds, and software version first. Replace the module only if the code returns with a healthy supply.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.