P0507 on Mercedes-Benz: How to Diagnose & Fix
Idle Air Control System RPM Higher Than Expected
1 Mercedes-Benz model · 1 documented issue · $320-$2,200 repair
P0507 on Mercedes-Benz by model: symptoms, diagnosis and fix
The integrated PCV / crankcase breather valve in the intake manifold (M274 2.0L turbo) commonly fails or its diaphragm tears, causing unmetered vacuum leaks. Oil mist can then migrate up the engine wiring harness via capillary action, contaminating connectors. Reported predominantly on 2016-2019 GLC 300 models. When ignored, lean running and loss of crankcase regulation risk further engine damage; in the worst cases the oil-soaked engine harness also requires replacement.
Common Symptoms
- Rough or unstable idle
- Check engine light
- Reduced fuel economy
- Whistling/hissing vacuum leak noise
- Oil in electrical connectors
How to Fix
Replace the PCV/crankcase ventilation valve (integrated into intake manifold/oil separator). If oil has wicked into the engine harness connectors, the affected harness section must also be replaced. Inspect connectors for oil intrusion at the same time.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mercedes-Benz M274 intake-line/crankcase-breather assembly A274090560080OEMMercedes-Benz A274090560080
Confirmed failed M274 intake-line/partial-load ventilation assembly branch for applicable 2015-2018 non-hybrid GLC300 Fitment/availability: The inspected direct U.S.
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Sources for this issue (2)
P0507 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0507 mean on a Mercedes-Benz?
P0507 stands for "Idle Air Control System RPM Higher Than Expected." This code means the engine is idling faster than the computer's target idle speed, typically by a set margin such as 200 RPM above commanded. The engine control module manages idle by metering a small amount of air around the throttle plate (via an idle air control valve or electronic throttle), and when it can't bring the RPM down to target it flags this code. The most common real cause is unmetered air sneaking into the intake — a vacuum leak — that the computer can't compensate for. It generally indicates extra air entering the engine or a problem with the idle/throttle control system. On Mercedes-Benz it is documented across 1 model: GLC.
What are the most common causes of P0507?
The most common causes of P0507 are: Vacuum or intake air leak (hoses, gaskets, intake boot), Dirty or sticking throttle body or throttle plate, Faulty or stuck idle air control valve, Leaking intake manifold or throttle body gasket, Stuck-open PCV valve or cracked PCV hose, Dirty mass airflow sensor giving false readings, Failing throttle position sensor, Leaking brake booster or its vacuum hose. The specific cause varies by vehicle.
How much does it cost to fix P0507 on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $320 to $2,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0507 on a different make?
View P0507 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.