Internal Control Module Keep Alive Memory (KAM) Error
Your engine's computer has corrupted memory that stores learned settings, like a notebook with smudged writing. The ECU can't remember critical adjustments it made to run smoothly, causing performance issues.
The ECU continuously writes adaptive data (fuel trim, idle corrections, shift points) to Keep Alive Memory powered by the battery. During startup and shutdown, the module performs checksum verification on this stored data. If bit corruption is detected during memory integrity checks, the fault sets.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| KAM Checksum Verification | Checksum matches stored value at power-up | Checksum mismatch detected; data integrity failure |
| Memory Write Integrity | Data successfully written and read-back verified | Write-verify failed; memory cell error |
Code P0604 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0604 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.