What causes engine light malfunction in the Mercedes C 300?
In this article, we find out what causes the engine light malfunction in the Mercedes Benz C 300 and answer the following questions: is the Mercedes C 300 reliable? Should you buy a used Mercedes Benz C 300?
What causes engine light malfunction in the Mercedes C 300?
The causes of the engine light malfunction in the Mercedes C 300 are listed below
- Mixture adaptation
- Combustion misfiring
- An abnormal noise from the engine
- Boost pressure too low form turbocharger
The 2010 Mercedes Benz C 300 was powered by an M272 engine which is a naturally aspirated 3.0 litre V 6 engine. M272 has a variable intake manifold with hot air mass flow sensor installed before the throttle valve.
The air mass sensor measures the air going into the intake manifold and as petrol engines are quantity controlled the fuel injected was determined by the air mass and engine load.
The intake manifold is connected to the intake ports and a gasket is installed between them which leaks as the mileage starts to increase. The leak in the intake manifold gasket causes un-metered air to enter the intake of the engine and affect the mixture formation.
The remedy was not expensive as the gasket cost was less and once the fault was rectified the vehicle was good for thousands of kilometres. The latest generation of the C 300 is powered by a 2.5 litres inline 4 cylinders M264 engine.
The M264 engine is turbocharged and the air mass is measured by the intake manifold pressure and temperature sensor. The intercooler is also liquid-cooled and Mercedes Benz has used special seals and located the intercooler very neat to the intake manifold so that there is no unmetered air going into the engine and disturbing the mixture adaptation.
The M264 is affected by mixture adaptation issues due to minute leaks in the intake and the exhaust valves. A cylinder leak test can determine which cylinder is leaking but the remedy is to renew the cylinder head and all the intake and exhaust valves.
The entire work of replacing the cylinder head is covered under warranty as Mercedes Benz offers a standard warranty of up to 5 years. But a manufacturing defect in the cylinder head is a critical issue and it certainly affected the reliability of the Mercedes Benz C 300.
Mercedes Benz uses special ignition coils with integrated output stages. This allows the engine control unit to reduce the dwell time of the coil and recharge it for multiple sparks. This mode is called a multispark mode, it creates multiple sparks in one ignition cycle and brings the engine to its operating temperature more quickly.
The multi-spark mode on the other hand also puts the spark plugs under great stress. Some spark plugs get affected due to extreme temperature and ceramic housing breaks. The broken ceramic housing also covers the electrode and causes the combustion misfiring. Replacing the affected spark plug is the only remedy and the fault does not occur again. Mercedes Benz also recommends replacing the spark plugs after completing 4 years or 60,000 km.
An abnormal noise from the engine
Many C 300 reported cases with abnormal engine noise with cylinder misfiring in multiple cylinders. The problem came due to worn-out gear on the balancer shaft which led to the incorrect position of the crankshaft to the position of the camshafts.
Only a certain number of engines were affected but the timing chain and balancer shaft are critical engine components and usually, they should not wear out.
Mercedes Benz engines are known to last long without any major repairs but the balancer shaft issue in the M272 damaged the reputation. Mercedes Benz quickly rolled out work instructions and rectified the issue by replacing the entire balancer shaft and setting the basic position of the camshaft. In some markets, the repair work was complete without cost to the customer.
Low boost pressure
The C300d model uses Mercedes Benz latest inline 4-cylinder diesel engine OM654. The OM654 engine is bi turbocharged and the low-pressure turbo is actuated electronically while the high-pressure turbocharger is wastegate controlled.
The vacuum cell on the wastegate is connected to the electronic boost pressure vacuum transducer. If there is a problem in the boost pressure transducer the wastegate of the turbocharger is designed to remain fully open and this results in low boost pressure.
The fault is rectified after replacing the boost pressure transducer which is actuated by the engine control unit via pulse width modulation.
Is the Mercedes C 300 reliable?
The old generation of the C class had many reliability issues due to malfunctions in the ABS/ESP control unit and abnormal noise from the engine. Mercedes Benz rectified all the reliability issues in the facelift of the Mercedes Benz C Class model series W205.
Both petrol and diesel engines are available in the C300 models, the diesel model is represented with the letter ‘d’ at the end. Many customers have driven their C class for more than 100,000 km without issues.
The C 300/300d is also an AMG line model meaning the exterior and interior styling is more sporty and similar to the high-performance version of the C class.
The charge air intercooler is also liquid-cooled in petrol as well as diesel engine, there is an independent secondary coolant pump with its coolant reservoir and electric coolant pump. The intercooler ensures hot changed air is cooled down before reaching the intake manifold.
The turbocharger on the C 300 is electronically actuated and the complete charger air system is very reliable compared to the predecessor M274 engine. Despite the engine malfunction issues, the C 300 is still a very reliable car and Mercedes Benz also offers extended warranty plans that can cover the vehicle for up to 6 years.
Should you buy a used Mercedes Benz C300?
Mercedes Benz C 300 is the best model in the C Class model series. It even comes in a 4Matic all-wheel-drive version. Mercedes Benz has a certified pre-owned car programme at the authorised dealerships, the certified pre-owned cars come with a 1-year standard warranty depending on the mileage of the vehicle.
Therefore buying a used Mercedes Benz C 300 is a great and affordable way to enter the world of premium luxury cars and experience comfort and performance.
Other articles about Mercedes Benz you may be interested in
Mercedes Benz C 300 has very few issues that cause engine light malfunctions and the latest model W206 C Class looks very reliable and the 2.0-litre M254 engine is based on the latest M256 inline 6 cylinder engine. Therefore, the issues in the older models will not occur in the latest Mercedes Benz C 300