P0604: RAM integrity checks cover several different memory paths

P0604 means the controller has detected a random-access-memory integrity problem. The cited ECM and TCM summaries include system RAM, cache RAM, timing-processor RAM and other protected or duplicated memory checks. It is an internal test category, not a fault assigned to an external sensor.

A shared code does not imply one threshold

For system RAM, the examples describe data read back differently from the data written. The first scan is expected to finish within thirty seconds, with background testing continuing afterward. A very brief post-clear observation may therefore miss the initial scan's completion.

The cache criteria illustrate module differences: the ECM page lists 254 mismatch counts, whereas the TCM page lists three. The TCM also describes disagreement between ordinary and duplicated data during updates. Borrowing one count or timing value for all P0604 applications would hide these distinct paths.

Interpreting the result

Start with the reporting module and any available internal failure detail. A code in the TCM cannot be assigned to the ECM simply because an inexpensive reader displays a generic engine-oriented description. The code also does not say which specific memory area failed unless additional module information identifies it.

The summary documents the self-tests but offers no repair sequence or blanket reprogramming remedy. Verification should follow that controller's service procedure and allow the relevant memory checks to complete under their specified conditions. Clearing the DTC and seeing normal external sensor data does not establish that internal RAM testing has passed.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 360. GM 2025-03a, page 1082.