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P0604 — Internal Control Module Random Access Memory Ram Error

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

The P0604 code indicates that the Powertrain Control Module (PCM) has detected a problem with its internal random‑access memory during a self‑check. It typically points to a memory fault inside the PCM or to a condition that disrupts its operation.

Symptoms

What causes it — most likely first

1. Faulty Powertrain Control Module (PCM)

Internal RAM failure within the PCM can trigger the random access memory error code.

2. Voltage or power supply issue to PCM

Fluctuations in supply voltage, a weak battery, or a failing charging system can cause RAM errors in the PCM.

3. Poor electrical ground or wiring connection to PCM

Loose, corroded, or damaged wiring and grounds can interrupt PCM operation and produce a RAM error.

4. Blown or faulty PCM power fuse/relay

A compromised fuse or relay may cut power to the PCM intermittently, leading to memory faults.

5. Low battery voltage or high system load

When system voltage drops below specifications, the PCM may misperform its self‑check and set P0604.

How it's diagnosed

  1. Check battery voltage and charging system performance with a multimeter.
  2. Inspect PCM power and ground circuits for corrosion, loose pins, or damaged wires.
  3. Verify that all relevant fuses and relays are intact and properly seated.
  4. Clear the code and perform a drive cycle to see if it returns.
  5. If the code persists, test the PCM for internal memory faults or consider replacement.

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 ErrorP0603 — Internal Control Module Keep Alive MemP0605 — Internal Control Module Read Only MemoP0606 — Control Module Processor

Vehicles this code applies to

The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:

2023 Buick Envision

Frequently asked

Do I need to replace the PCM to fix P0604?

Replacing the PCM is seldom required; most often the fault stems from power, wiring, or voltage issues that can be repaired without swapping the module.

Can a bad battery cause this code?

Yes, low battery voltage or a failing alternator can cause the PCM to register a RAM error during its self‑diagnosis.

Will disconnecting the battery erase the code?

Disconnecting the battery may clear the code temporarily, but it does not address the underlying cause and the code may reappear if the fault persists.

Is there a recall or service bulletin for P0604?

No widespread recall exists for this code; repairs focus on diagnosing power and wiring problems.