Powertrain, generic · Computer and auxiliary outputs

P0604 Internal Control Module Random Access Memory (RAM) Error

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0604 means the module's working memory (RAM) failed its self-test: a value written to a cell does not read back correctly, a built-in hardware test fails, error correction reports faults, or protected memory is written without permission. GM's engine module scans the whole RAM within 30 s of start-up and then keeps checking in the background, setting the code after repeated failures with the lamp in the first trip; Ford tests RAM during initialisation, the GM gateway with error correction at start (two trips). Unlike most memory codes, P0604 is used the same way by GM, Ford, Chrysler and Saab. Consequences depend on the module: a transmission module goes into limp mode with maximum line pressure and a fixed gear, an engine module may reduce power. The code alone does not say which module set it – the scan tool shows whether it is the engine, transmission, brake or body module.

Likely causes

Internal hardware defect of the module (RAM)
Low voltage, voltage dips or a poor ground or supply at the module
Faulty module software (update available)
Moisture or corrosion in the module or at its connector

Symptoms

  • Check engine light on
  • Limp mode or transmission limp mode
  • Intermittent stalling or starting problems
  • Several module codes at the same time

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine control modulecontrol module power supplycontrol module ground

Related codes

P0601P0603P0605P0606P0607P062F

References: law.cornell.edu, gsi.ext.gm.com, newtonnet.co.uk, saabwisonline.com.