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P codepowertrainMedium severity

P0603Internal Control Module Keep Alive Memory (KAM) Error

The engine computer has lost or corrupted the learned data stored in its keep-alive memory.

Definition

The PCM stores adaptive data such as fuel trims, idle learn values, and transmission adapts in keep-alive memory (KAM), which is preserved by a constant battery feed when the ignition is off. P0603 sets when the module performs its self-check and finds the KAM contents invalid or erased. Symptoms can include rough idle, hesitation, or odd shifting while the module relearns, and the MIL may illuminate. The most common trigger is a battery disconnect or low-voltage event, but a repeated fault points to a wiring or module problem.

Common causes

  • Recent battery disconnect, dead battery, or jump-start that erased keep-alive memory
  • Open or intermittent constant (KAM) battery feed circuit or blown fuse to the PCM
  • Loose or corroded battery terminals or PCM grounds causing voltage dropouts
  • Voltage spikes from jump-starting, welding on the vehicle, or a failing charging system
  • Internal PCM memory failure
  • Aftermarket accessory wiring backfeeding or interrupting the PCM's constant power

Common misdiagnoses

  • Replacing the PCM when the real fault is a blown keep-alive fuse or corroded feed circuit
  • Replacing the battery when terminals or grounds are the actual problem
  • Chasing driveability parts (sensors, injectors) for symptoms caused by lost adaptive memory
  • Replacing the alternator for a one-time voltage event

Troubleshooting steps

  1. 1.Establish the history

    Ask whether the battery was recently replaced, disconnected, or jumped; a single occurrence after such an event can simply be cleared and monitored.

  2. 2.Check the PCM keep-alive fuse and feed

    Verify battery voltage on the PCM's constant power pin with the key off and inspect the fuse; a missing feed guarantees the code returns every key cycle.

  3. 3.Load-test the battery and inspect connections

    Confirm the battery passes a load test and that terminals and PCM ground eyelets are clean and torqued, since brief dropouts corrupt KAM.

  4. 4.Wiggle-test the harness

    Monitor PCM battery voltage on a meter while flexing the harness and tapping connectors to expose intermittent opens.

  5. 5.Clear the code and re-evaluate

    Clear KAM, complete a drive cycle so adapts relearn, and only suspect the PCM itself if the code resets with power and grounds verified good.

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