P0018 on Mercedes-Benz: How to Diagnose & Fix
Crankshaft/Camshaft Position Correlation - Bank 2 Sensor A
3 Mercedes-Benz models · 3 documented issues · 2 critical · $250-$6,500 repair
P0018 on Mercedes-Benz by model: symptoms, diagnosis and fix
On the M276 3.5L V6 (and the related M278 V8) the four camshaft adjusters — the variable-valve-timing phasers bolted to the ends of the cams — wear internally. The locking pin and vane chambers lose their ability to hold position, and oil bleeds out of the adjuster while the car sits. On the next cold start the cam is unsupported for the first second or two of cranking until oil pressure builds, producing a loud metallic rattle from the front of the engine. As wear progresses the adjuster can no longer hold commanded timing and the ECU logs cam/crank correlation and timing-over-advanced faults. Clogged camshaft adjuster magnets (solenoids) and a stretched timing chain often accompany the failure and are commonly misdiagnosed as the sole cause. Owners frequently report the dealer first replacing solenoids or doing an oil change before the adjusters themselves are condemned.
Common Symptoms
- Loud metallic rattle for 1-3 seconds on cold start
- Rattle worse after the car sits overnight or several days
- Check engine light
- Rough idle when cold
- Reduced power / limp mode in advanced cases
- Noise diminishes once oil pressure builds
How to Fix
Replace the camshaft adjusters — all four, not just the noisy bank — with the updated Mercedes parts, along with the camshaft adjuster magnets/solenoids. Inspect the timing chain, tensioner and guide rails while the front cover is open and replace them if the chain shows stretch, since a worn chain will destroy new adjusters. The engine must be re-timed and the adaptations reset. Use only the specified MB 229.5/229.51 oil at the correct viscosity and keep to shorter oil-change intervals, as degraded oil accelerates adjuster wear.
Sources for this issue (3)
The M278 4.7L biturbo V8 used in the GLE 550 4MATIC (W166/C292) has a complex timing drive with one primary chain and two secondary chains, each with its own tensioner. On early engines the secondary chain tensioners lose oil pressure during shutdown because they lack anti-drainback check valves, so on cold start the chains and camshaft adjusters run momentarily dry and rattle loudly for the first 2-5 seconds until oil pressure builds. Left unaddressed, chain slack, worn guide rails, and worn camshaft adjusters can advance to camshaft-correlation faults and, in the worst case, timing jump. This is distinct from the M276 V6 camshaft-adjuster rattle: it is the V8 M278's multi-chain oil-starvation design, and Mercedes issued a service fix (TSB LI05.10-P-056435) adding oil check valves plus revised secondary tensioners for engines up to a specific engine-number cutoff (278 9xx).
Common Symptoms
- Loud rattle or chatter for the first 2-5 seconds on cold start
- Metallic timing-chain/rattle noise from front of engine
- Check engine light with camshaft/crankshaft correlation codes in worse cases
- Noise diminishes once oil pressure builds
How to Fix
Install the revised secondary timing chain tensioners together with the oil anti-drainback check valves in the cylinder-head oil passages per the Mercedes service procedure; inspect and replace worn chain guide rails and the camshaft adjuster (solenoid) units as needed. If the primary chain is stretched, a full timing chain/guide service is required. Verify no cam/crank correlation codes remain after repair.
Sources for this issue (4)
The gasoline X166 GLS engines - M276 3.0 biturbo V6 (GLS 450), M278 4.7 biturbo V8 (GLS 550) and M157 5.5 biturbo V8 (AMG GLS 63) - share a well-documented failure where the seals inside the camshaft adjuster magnets (solenoids) and camshaft position sensors give up and pressurized oil is pushed into the sensor's electrical connector. From there the oil wicks along the wire strands into the main engine harness and can reach the ECU and other connectors. Early signs are oil in the cam-magnet plug and a wet valve-cover area; if ignored it produces cam-timing faults (P0016-family and P06DA-type codes), rough running and a harness or ECU replacement bill. MBWorld threads document dealers resealing solenoids under warranty and owners asking Mercedes for a campaign that was never issued.
Common Symptoms
- Oil inside camshaft magnet or cam sensor electrical connector
- Oil seeping at the front of the valve cover
- Check engine light with camshaft correlation codes
- Rough idle or misfire after oil reaches other connectors
- Oil found inside ECU connector
How to Fix
Replace the leaking camshaft adjuster magnet(s) and/or cam sensor with the current revised part and, if any oil is in the connector, install the Mercedes harness-extension 'pigtail' repair sections so the contaminated section is cut out and the oil cannot migrate further. Check the connectors at every oil change on these engines. Solenoid plus pigtail is about $250-600 per position; if the harness or ECU is already saturated, $2,000-4,500. No recall or extended warranty exists.
Sources for this issue (4)
P0018 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 P0018 mean on a Mercedes-Benz?
P0018 stands for "Crankshaft/Camshaft Position Correlation - Bank 2 Sensor A." This code means the computer detected that the crankshaft and the Bank 2 'A' (typically intake) camshaft are out of their expected timing relationship. The computer compares the crankshaft and camshaft position sensor signals; they should stay in a fixed correlation as the engine turns. When the Bank 2 camshaft is too far off from the crankshaft, P0018 sets, indicating the valve timing on that bank is misaligned. This can cause rough running, reduced power, hard starting, or a no-start, and in some cases signals timing chain or phaser trouble that warrants prompt attention. On Mercedes-Benz it is documented across 3 models: E-Class, GLE, GLS.
What are the most common causes of P0018?
The most common causes of P0018 are: Stretched, worn, or jumped timing chain (Bank 2), Worn or broken timing chain guides/tensioner, Stuck variable valve timing solenoid or phaser, Low or dirty engine oil affecting the phaser, Faulty crankshaft or camshaft position sensor, Damaged reluctor/tone ring, Incorrect timing from prior service, Wiring or connector fault at a cam/crank sensor. The specific cause varies by vehicle.
How much does it cost to fix P0018 on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $250 to $6,500 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 P0018 on a different make?
View P0018 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.