OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P0604

Internal Control Module Random Access Memory (RAM) Error

ECU self-test detected a RAM fault during runtime checks. This is an internal ECU defect; replacement or reflash with manufacturer support is generally required.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number6 / 04

Possible causes

  • ECU internal RAM fault high
  • Module software outdated, reflash may resolve low
  • Supply voltage outside specification low

Symptoms

  • Check engine light on
  • Possible limp mode or no-start
  • Multiple follow-up faults across modules
  • Reset/relearn may be needed after repair

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 400–2000 €
  • Estimated time: 1–4 h
  • Component: ecm
  • MIL / check engine light
  • limp mode possible

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication