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P0603 — Internal Control Module Keep Alive Memory Kam Error

Generic OBD-II · all makesPowertrain (engine & transmission)

The P0603 code indicates that the engine computer (PCM) has detected an error in its Keep Alive Memory (KAM), which requires continuous battery power to retain learned operational data. This typically happens when constant power to the PCM is interrupted, rather than the computer itself failing. In most cases, the root cause is a power supply issue, a dead battery, or a blown fuse, not a defective module.

Symptoms

What causes it — most likely first

1. Battery disconnect or dead battery

If the battery is disconnected, replaced, or drops below the minimum voltage, the PCM loses power to the KAM, triggering this code.

2. Blown KAM power fuse or open circuit

A dedicated fuse supplies constant 12-volt power to the PCM for memory retention; if this fuse blows, the memory resets and sets the code.

3. Corroded or loose battery terminals

Poor electrical connections at the battery can interrupt the constant voltage feed to the PCM during cranking or operation.

4. Wiring or connector damage

Frayed, corroded, or broken wiring in the constant power circuit between the battery and the PCM can cause intermittent power loss.

5. Aftermarket tuner or programmer interference

Plug-in tuning devices can alter or corrupt the PCM's memory, causing the system to flag a KAM error.

6. Internal PCM failure

Though rare, an internal fault within the PCM's memory circuit can prevent it from retaining data when power is continuous.

How it's diagnosed

  1. Verify if the battery was recently disconnected, replaced, or went completely dead; if so, clear the code and see if it returns after a drive cycle.
  2. Inspect battery terminals for corrosion or looseness, and perform a load test to ensure the battery maintains proper voltage.
  3. Locate and test the dedicated Keep Alive Memory fuse in the power distribution box, replacing it if it lacks continuity.
  4. Check for aftermarket tuning devices plugged into the OBD-II port and remove them to see if the code clears.
  5. Perform a visual inspection of the PCM wiring harness, specifically checking the constant power and ground wires for chafing or damage.
  6. If all power, ground, and wiring circuits test normal and the code persists immediately after clearing, suspect an internal PCM fault.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0600 — Serial Communication LinkP0601 — Internal Control Module Memory ChecksuP0602 — Control Module Programming ErrorP0604 — Internal Control Module Random Access P0605 — Internal Control Module Read Only MemoP0606 — Control Module Processor

Frequently asked

Does a P0603 code mean I need to replace my engine computer?

No, rarely. Many drivers and inexperienced technicians mistakenly replace the PCM for this code, but the actual cause is almost always a loss of constant battery power, a blown fuse, or a poor connection. Replacing the computer will not fix a wiring or power supply issue.

Can I still drive my vehicle with a P0603 code?

Yes, the vehicle is generally safe to drive, but it may run poorly or shift harshly at first. Because the Keep Alive Memory was erased, the engine computer has lost its learned adaptations and will need to relearn your driving habits over a few drive cycles.

Will disconnecting the battery clear this code?

Disconnecting the battery is actually what causes this code in the first place. While it will clear the code from the screen, it also erases the memory again. The code should only be cleared with a scanner after the underlying power supply issue is fixed.

How do I fix a P0603 code?

Start by checking the battery condition and ensuring the terminals are clean and tight. Then, locate and test the dedicated KAM power fuse for the PCM. If the fuse and battery are fine, inspect the wiring for damage before ever considering a computer replacement.