P0605 Code: Control Module ROM Error — Causes & Fix
P0605 means the ECM/PCM failed an internal ROM (read-only memory) self-test — corrupted program memory in the control module.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $60 – $900
- Time to fix
- 1–4 hours
What it means
Causes include corrupted firmware, an internal module fault, or power/ground problems during programming. P0605 is a generic OBD-II code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer OBD-II vehicle regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Poor running or no-start
- Limp mode
How to fix it
- 1
Verify power and grounds
1. Check ECM power and grounds and charging voltage.
- 2
Reprogram or replace
1. Reflash the module if supported; otherwise replace it. 2. Clear the code after repair.
Frequently asked questions
Is P0605 the same as P0601?
They are related internal-memory faults — P0601 is a checksum error, P0605 is a ROM fault. Both point at the module after ruling out power/grounds.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.