Powertrain, generic · Computer and auxiliary outputs

P0605 Internal Control Module Read Only Memory (ROM) Error

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0605 reports an error in the module's program memory (ROM, today flash), found by a checksum or error-correction check at start-up or in the background. Ford is the main user: its engine and transmission modules compare a ROM checksum and set P0605 with the check engine light; the diesel transmission module tests once per trip at start. GM's engine module does not use P0605 and reports the same fault as P0601; the GM gateway (2025) uses it for uncorrectable ROM bit errors with two-trip logic, and GM Europe's 1.6 L engine even assigns it to processor faults of the throttle control. Which of P0601 and P0605 appears is therefore the manufacturer's choice. The usual repair is reprogramming, which restores the memory contents; replace the module only if the code returns.

Likely causes

Program memory corrupted by an interrupted reflash
Internal flash or ROM defect
Faulty module software (update available)
Low voltage, voltage dips or a poor ground or supply at the module

Symptoms

  • Check engine light on
  • Possibly starting problems
  • Transmission limp mode if the transmission module is affected
  • Reduced power (GM Europe assignment)

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.

What to check first

  1. Reprogram the module
  2. Replace if the fault returns

Parts involved

engine control modulecontrol module power supplycontrol module ground

Related codes

P0601P0602P0604P0606P0613

References: law.cornell.edu, newtonnet.co.uk, fordservicecontent.com, roushcleantech.com.