P0300 on Mercedes-Benz
Random/Multiple Cylinder Misfire Detected
P0300 on Mercedes-Benz vehicles indicates random/multiple cylinder misfire detected. Au7o has documented this code across 3 Mercedes-Benz models — most commonly on A-Class, G-Class, GLB. P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. Typical repair costs on Mercedes-Benz range from $300 to $20,000, depending on the specific model and root cause.
Common Causes of P0300
- •Worn or fouled spark plugs (across cylinders)
- •Vacuum or intake air leak
- •Weak fuel pump, clogged fuel filter, or low fuel pressure
- •Failing ignition coils or worn spark plug wires
- •Dirty or faulty mass airflow (MAF) sensor
- •Clogged or dirty fuel injectors
- •Faulty crankshaft/camshaft position sensor
- •Low compression or EGR/PCV system faults
P0300 on Mercedes-Benz by Model
Mercedes-Benz A-Class(1 issue)
- M282 1.3L Intake Valve Carbon Buildup2019-2023
The 1.3L turbocharged direct-injection M282 engine (co-developed with Renault, used in A180/A200) suffers carbon deposit buildup on the intake valves and ports because direct injection does not wash the valve backs with fuel. On urban/short-trip duty cycles deposits accumulate from roughly 60,000 miles, causing rough running and hesitation.
Mercedes-Benz G-Class(2 issues)
- M177 4.0L Twin-Turbo V8 Excessive Oil Consumption and Cylinder Scoring2019-2025
The 4.0L biturbo M177 V8 in the W463A G 550 and AMG G 63 is documented for above-normal engine oil consumption (often 1 quart per ~1,000-2,000 miles in worse cases), with the most severe outcome being cylinder bore/liner scoring and piston ring wear at higher mileage. The high-output, hot-running twin-turbo design stresses piston rings and the iron-coated aluminum bores; carbon buildup and ring coking aggravate consumption. If left unaddressed, low oil level can lead to bearing/piston damage. Owners report repeated low-oil warnings between services and, in advanced cases, misfires and blue exhaust smoke.
- M157 5.5L Biturbo V8 Cylinder Scoring and Camshaft Adjuster Wear (Pre-Facelift G 63)2013-2018
The 5.5L M157 biturbo V8 used in the W463 AMG G 63 before the 2019 redesign is documented for cylinder wall scoring/scuffing at higher mileage plus weaknesses in timing-chain components and camshaft (VVT) adjusters. The camshaft adjuster magnets/solenoids meter oil to the VVT and chain; restricted flow accelerates chain and gear wear. Oil intrusion into the camshaft position sensor wiring can also mimic internal engine faults. Symptoms range from multi-cylinder misfires to rattle and, in worst cases, metal in the oil from bore scoring.
Mercedes-Benz GLB(2 issues)
- Carbon Buildup on Intake Valves (Direct-Injection M260) Causing Rough Idle and Power Loss2020-2024
Like other Mercedes direct-injected turbo engines, the M260 in the GLB (and the 1.3L M282 in the GLB 180/200) accumulates carbon deposits on the intake valves and intake tract over time because fuel is injected directly into the cylinder and never washes the back of the valves. This leads to unstable idle, hesitation, reduced power and worse fuel economy as mileage climbs, and German sources note the 1.3L can also develop coked injectors. It is a wear/maintenance issue, not a recall.
- M260 Cylinder Head Exhaust Valve Seat/Guide Wear (Misfires, Compression Loss)2020-2022
The 2.0L turbo M260 four-cylinder used in the GLB 250 / GLB 35 (and the M264-related variants) suffers from premature wear of the exhaust valve seats and valve guides. The exhaust valves stop sealing, causing loss of compression in one or more cylinders, rough running and misfires. Mercedes acknowledged this as a manufacturing defect and issued a voluntary extended warranty in the US and Canada covering cylinder head replacement for up to 15 years / 150,000 miles on affected 2019-2022 A-Class, CLA, GLA and GLB vehicles. A 2026 NHTSA-posted TSB (MC-11028267) documents the valve seat/guide wear on M260/M264 engines. Left unaddressed it can progress to catastrophic piston/secondary damage that is NOT covered by the warranty extension.
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View P0300 across all makes →Frequently Asked Questions
What does P0300 mean on Mercedes-Benz?▼
P0300 stands for "Random/Multiple Cylinder Misfire Detected." P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. On Mercedes-Benz specifically, this code is documented across 3 models.
What causes P0300 on Mercedes-Benz vehicles?▼
Common causes on Mercedes-Benz: Worn or fouled spark plugs (across cylinders), Vacuum or intake air leak, Weak fuel pump, clogged fuel filter, or low fuel pressure, Failing ignition coils or worn spark plug wires, Dirty or faulty mass airflow (MAF) sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0300 on a Mercedes-Benz?▼
Repair costs on Mercedes-Benz range from $300 to $20,000, depending on the specific model and root cause.
Which Mercedes-Benz models have P0300 documented?▼
Au7o has documented P0300 on 3 Mercedes-Benz models: A-Class, G-Class, GLB.