P0606 fault code: ECM/PCM Processor

P0606 means “ECM/PCM Processor” — a computer and output circuits fault in the powertrain.

Can I DIY?

Professional-only boundary. You may confirm P0606 and list companion codes; processor or module work is professional only.

Do not DIYReviewed page boundary
ToolsSpecialist equipment

This is the conservative boundary from the reviewed code record. This page has no frozen site-wide safety grade, so it does not publish a repair route.

What to tell the garage about P0606

Stop driving now. The engine computer has detected a fault in its own processor. This is an internal control-module problem, not a sensor you can identify from a generic parts list on this page.

Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.

  • ECM/PCM Processor: Registration number
  • ECM/PCM Processor: Exact code P0606 and any companion codes
  • ECM/PCM Processor: Whether the engine management light is steady or flashing
  • ECM/PCM Processor: Whether the engine starts, runs, or other warning lamps are on
P06xxComputer and output circuits
MOT fail riskif the warning light stays on

What does P0606 mean?

P0606 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P06xx block, which covers computer and output circuits. The stored description is “ECM/PCM Processor”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0606 fail an MOT?

If the malfunction indicator lamp is illuminated when P0606 is stored, DVSA treats that as a Major defect (test fail) until the fault is repaired and the lamp remains off. A processor fault that leaves the malfunction lamp on is still a Major defect, independent of any module programming the tester cannot see.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

Related guides

Car diagnostic test cost: compare the scopeUK booking marketplaces currently publish diagnostic averages of about £52–£65. Engine management light on: steady or flashing?A steady engine management light means the computer has stored a fault. Drive with caution and get the code read. A flashing light is different — stop when it is safe.
P0600Serial Communication Link P0601Internal Control Module Memory Check Sum Error P0602Control Module Programming Error P0603Internal Control Module Keep Alive Memory (KAM) Error P0604Internal Control Module Random Access Memory (RAM) Error P0605Internal Control Module Read Only Memory (ROM) Error P0607Control Module Performance P0608Control Module VSS Output 'A'

P0606 — quick answers

Is it safe to drive with P0606?

Stop driving now. We have no verified driving guidance for P0606. Treat as do not drive until checked. Stop at once if the engine cuts out, will not restart, or several warning lamps come on together.

Will P0606 fail my MOT?

If the malfunction indicator lamp is illuminated when P0606 is stored, DVSA treats that as a Major defect (test fail) until the fault is repaired and the lamp remains off. A processor fault that leaves the malfunction lamp on is still a Major defect, independent of any module programming the tester cannot see.

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.