The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0308.
DTC/P0308·Mercedes-Benz
P0308 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveMercedes-Benz
P0308 on a Mercedes-Benz means the engine computer has detected repeated misfires on cylinder 8. Only engines with eight or more cylinders can set it, so it belongs to V8s, V10s and V12s. Cylinder 8 usually sits at the back of the engine next to the bulkhead, and the most common causes are the spark plug or ignition coil on that cylinder, then the injector, an intake leak or low compression.
Typical repair cost, all makes€55 - €2700
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Mercedes-Benz S500 / S550 (W221, M273 V8)
2005-2011The M273 V8 uses port injection, so intake-valve carbon is rarely the reason for a single-cylinder misfire; coil, plug and injector come first. The M273 can also wear the sprocket on its timing-chain idler gear, which upsets camshaft timing and sets codes P0016 to P0019; if one of those is stored with the P0308, the timing needs attention before the ignition.
What causes P0308 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0308 page, these are the patterns noted for Mercedes-Benz models:
Mercedes-Benz S500 / S550 (W221, M273 V8)Worn spark plug or failing coil on cylinder 8
Mercedes-Benz S500 / S550 (W221, M273 V8)Worn timing-chain idler sprocket upsetting camshaft timing
How to diagnose P0308 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0308:
- Read all stored and pending codes and the freeze frame. Check the engine speed, load and temperature when the misfire was logged: cold-only misfires often point to fuel or a cracked plug, hot-only misfires more often to a coil breaking down with heat.
- Locate cylinder 8 using the service data for your engine. On GM V8s it is the rearmost cylinder on the right bank, on Ford V8s the rearmost cylinder on the left bank; European makers use their own numbering.
- Remove the cylinder 8 coil and look into the plug well for oil or water, then pull the plug and check its gap, electrode wear and insulator.
- Swap the cylinder 8 coil with a neighbouring cylinder, clear the codes and drive. If the misfire follows the coil, the coil is faulty.
- If the misfire stays on cylinder 8, test the injector: check its connector, listen for it on a port-injected engine, or have a workshop test a direct injector.
- Look at the long-term fuel trim on the bank containing cylinder 8. A lean trim on that side only suggests an intake leak near the rear of the manifold; confirm it with a smoke test.
- Run a compression test on cylinder 8 and compare it with the others, followed by a leak-down test if it reads low, to separate valve trouble from worn rings.
- After the repair, clear the codes and complete a drive with idle, steady cruising and acceleration to confirm the misfire is gone.
How much does P0308 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0308 in EUR, compiled across makes. Expect Mercedes-Benz parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0308
These codes are often seen alongside P0308 or point to related issues, on any make:
Looking for the full P0308 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0308 guideSkanyx · Mercedes-Benz
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