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OBD-II · Engine and powertrain (P)

P0605

Internal control module read only memory (ROM) error

What it means

The ECU's self-check found an error in its program memory.

Symptoms

  • engine warning light
  • possible limp mode, stalling or no start
  • sometimes no noticeable change

Likely causes, most likely first

Likely causes, most likely first
No.Cause
01low or unstable supply voltage (weak battery, poor earths, jump-starting)
02interrupted or failed software update or remap
03water ingress into the ECU or its connector
04internal ECU failure

What to check, step by step

  1. 01Check the battery, charging voltage and the ECU power supplies and earths
  2. 02Clear the code and see whether it returns
  3. 03Inspect the ECU and its connectors for water ingress or corrosion
  4. 04Check for a software update from the maker, or whether the ECU has been remapped
  5. 05Reprogram the ECU with a stable power supply connected, or repair/replace it (a replacement usually needs coding and immobiliser matching)