Mercedes-Benz P0507

Idle speed higher than expected on Mercedes — M271/M274/M276 PCV diaphragm and vacuum hose.

Mercedes-Benz P0507 — Idle speed higher than expected on Mercedes — M271/M274/M276 PCV diaphragm and vacuum hose. Typical UK independent garage cost: £180–£580.

What actually causes P0507 on a Mercedes-Benz

Mercedes P0507 is PCV-related — diaphragm in the rocker cover or a perished vacuum hose. M271 cam cover is the famous one.

Mercedes-Benz engines that log P0507

• M271 1.8 Kompressor/turbo
• M274 2.0 turbo
• M276 3.5 V6

How we diagnose P0507 on a Mercedes-Benz

1. Smoke-test intake
2. Oil filler suction test
3. Rocker cover PCV inspection

The common misdiagnosis to avoid

Cheap aftermarket M271 cam covers fail. Mercedes OE or quality Vaico only.

Mercedes-Benz P0507 repair cost in the UK

Expect £180–£580 including parts and labour at an independent garage. Main-dealer quotes on Mercedes-Benz are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

M271 P0507 — cam cover with PCV. £180 part, hour's work.

Codes usually seen alongside P0507 on Mercedes-Benz

• P0171

Symptoms drivers report with P0507

• The car feels like it's 'creeping' forward too fast at traffic lights without touching the gas.
• Engine revs stay hung up at 1200rpm when you dip the clutch approaching an intersection.
• A noticeable 'hissing' or whistling noise from the engine bay when idling on the driveway.
• The stop-start system has stopped working because the idle isn't stable enough for the ECU.
• Surging or 'hunting' revs when you first start it from cold in the morning.

Repairs that clear P0507

• Smoke-test intake
• Clean throttle body
• Replace PCV valve / rocker cover
• Inspect all vacuum hoses

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0507 guide.

Reading P0507 on a Mercedes-Benz properly

A generic reader will show P0507 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Mercedes-Benz has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0507 without fixing it

Erasing the code resets the Mercedes-Benz's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0507 is showing on your Mercedes-Benz, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.