Code Definition

P0604 — Internal Control Module Random Access Memory (RAM) Error

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0604

P0604 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0604 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

Random access memory inside the Engine Control Module holds the temporary working data the processor uses during operation, including live sensor values, calculated fuel and timing corrections, adaptive learning values, and intermediate results from the module's diagnostic routines. The module runs continuous self tests on this memory, writing known patterns to memory locations and reading them back to confirm every cell stores and returns data correctly. DTC P0604 sets when one of these read and write checks fails, indicating a memory location that cannot reliably hold data, which the module ...

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