What is the engine warning light on a Mercedes W204?
The check engine light illuminates on the Mercedes C-Class W204 usually to indicate a problem with the engine management system. This system monitors various engine sensors and components to ensure that everything is functioning correctly and according to the manufacturer’s specifications.
What is the most common reason for the check engine light to come on?
There are several reasons why the check engine light may come on in the Mercedes C-Class W204, including:
- A faulty sensor: If any of the engine sensors are not functioning properly, it can cause issues with the engine management system, which may result in the engine light coming on.
- A faulty exhaust system: If your car’s exhaust system is faulty, it can lead to problems with exhaust gas pressure, which may trigger the engine light.
- A dirty air filter: A dirty air filter can lead to insufficient air supply to the engine, causing combustion issues, which can in turn trigger the engine light.
- A problem with the fuel system: If your car’s fuel system is faulty, it can result in inadequate combustion or fuel overconsumption, leading to the engine light coming on.
Case study : How to reset engine light on Mercedes W204 ?
Check engine light Mercedes C-Class W204
This issue under investigation is well-known among Mercedes C-Class vehicles equipped with the M272 engine.
A customer owns a Mercedes C-Class W204 equipped with a 6-cylinder engine M272. Lately, he notices a delay in starting when cold. A qualified Mercedes technician intervenes using diagnostic equipment and finds fault codes 1200 and 1208 recorded in the engine electronic control unit.
Note:
The fault codes are recorded as current in the fault memory. After clearing the fault memory followed by engine start-up, the fault codes reappear immediately.
After analyzing the error codes, the technician suggests that the Counterbalance Shaft Gear or the Timing Chain Guide Gear is worn out (chain gear type of fault).
Note:
The position of the camshafts on the right bank of cylinders in relation to the crankshaft is obstructed by a worn gear on the counterbalance shaft or by a worn guide gear on the timing chain.
Check carried out by the technician
Wear inspection with endoscope.
- Insert the endoscope through the chain slider on the right side until reaching the counterbalance shaft / guide gear.
The reference image
Images of examples: Counterbalance shaft gear (chain gear without fault)
Type of chain sprocket damage
What the technician should do
- Remove the front right cover.
- Inspect the wear of the counterbalance shaft gear (engine 272) or the timing chain guide gear with a flexible endoscope (type of damage: chain gear / image with endoscope chain gear).
- In case of wear corresponding to the chain gear fault type: proceed to work sequence 4.
In the absence of chain gear wear, continue the diagnostic.
How do you fix a Mercedes check engine light?
- Replace the counterbalance shaft or the timing chain guide gear.
- Replace the chain tensioner (replace the chain tensioner only if necessary).
- Engine oil change and replacement of the oil filter.
- Drive the engine under high load and high RPM on a journey of at least 20 km.
Don’t Forget !!!
After replacement, you must:
- Change engine oil and replace oil filter!
- Replace the camshaft timing solenoids!
The engine repair must be carried out at a Mercedes Benz dealership with qualified system technicians and genuine spare parts.
Can you drive with engine light?
In the case study above, it’s imperative to cease driving the vehicle immediately upon the illumination of the check engine warning light on the dashboard Mercedes C-Class. Ignoring this warning could lead to potential damage to the engine over time. Continuing to operate the vehicle under such conditions poses significant risks, including exacerbating the underlying issue and potentially causing irreparable harm to the engine. Seeking prompt professional assistance from a qualified mechanic or authorized service center is crucial to diagnose and address the root cause of the warning light, ensuring the vehicle’s continued safety and optimal performance.
Safety rules
Use high-quality tools and equipment to avoid any risk of error or equipment breakdown during the repair.
When working under the hood, ensure the engine has cooled sufficiently to prevent burns.
Always follow the instructions in the owner’s manual or repair manual to ensure you are performing the repair correctly. If you are unsure about anything, consult a qualified mechanic for assistance.
Lastly, never attempt to repair a Mercedes engine if you are not trained or qualified to do so. Improper repairs can cause further damage and jeopardize your safety.
