What does a check engine light mean in a Mercedes Sprinter van?

This article will answer the following questions: what does engine light malfunction mean in a Mercedes Benz sprinter? What are the common causes and remedies for the engine light malfunction in the sprinter? 

What does a check engine light mean in a Mercedes Sprinter van?

Check engine light or EOBD light in a Mercedes Benz Sprinter means there is a malfunction in the engine and the engine performance will be poor or even reduced. Engine light malfunction is not just limited to the engine, it covers the complete drivetrain and its various sensors.

All the latest Mercedes Benz sprinters have electronic injection systems controlled by the engine or CDI control units. The CDI control unit is constantly monitoring parameters like the intake air mass, temperature and the amount of oxygen present in the exhaust system.

In addition to monitoring these parameters which are important for the operation of diesel engines, Mercedes Benz sprinters also get exhaust gas after-treatment systems like selective catalytic reduction and AdBlue injection. The engine light turns on if the SCR control unit detects a fault in the exhaust gas after the treatment system.

To check the fault and find out its cause, A fault code is generated according to the affected system. The fault code is then stored permanently in the fault memory of the engine control unit. Mercedes Benz sprinter also has a more advanced monitoring system that can also record the fault frame freeze data which is the condition when the fault code was generated.

The nature of the fault code can be current and stored meaning the fault is still present in the system and the performance of the vehicle will be affected or simply stored, which means the fault has occurred but all the systems like the fuel system, charge air system are functioning normally. The performance of the vehicle is not affected.

When there are current and stored fault codes, the time required for the diagnosis is fast. If the fault code is stored, the engine control unit detects the fault if the vehicle has not been reported to the workshop within 40 ignition cycles.

The stored fault codes are sporadic and it can take slightly longer to recreate the fault and identify the cause of the fault code. The Mercedes Benz CDI control unit is connected to the transmission control unit and the powertrain control unit on a CAN network. 

When the ignition is turned ON and all the control units acknowledge the start enable signal, the engine light turns off after a couple of seconds if there are no fault codes in the system.

What are the common causes and remedies for the engine light malfunction in the Sprinter?

The Mercedes Benz sprinter is a van used for different purposes like cargo delivery or people mover. The engine control units and the vehicle onboard electrical systems are fairly similar to the Mercedes Benz passenger cars. The Mercedes Benz Sprinter is powered by the inline 4 and V6 or inline 6 turbo diesel engines. The common causes and remedies for engine light malfunction are as follows:

  • Improper combustion

Improper combustion means there is still fuel in the exhaust system after the power stroke is completed. Mercedes Benz injectors are capable of five injections per power cycle. As diesel is self-igniting fuel, the injector performs pre and post-injections to completely burn the diesel and also reduce the formation of the NOX.

A faulty injector can cause an incorrect quantity of fuel to be injected into the cylinder and even though diesel engines always have more concentration of air, the incorrect quantity will cause combustion misfiring and black smoke from the exhaust.

To rectify the fault injectors it is possible to check the injection quantity in the engine control unit by connecting the Xentry diagnosis tool to the vehicle. The Xentry diagnosis tool also allows you to take a contact test of the injector. The contact test actuates the injector for a few seconds and the technician can confirm if the injector is working or not by checking the actual values and listening to the actuation noise.

After the new injector is installed and coded into the engine control unit, a vehicle road test is performed to confirm if the fault is rectified successfully or not.

  • An incorrect signal from the sensors

Mercedes Benz engines rely on the signal from various temperature and pressure sensors to operate the actuators. Every sensor is like the air mass sensor, the outside air temperature sensor and boosts pressure sensor must provide the correct signal in the specified range. 

When there is a fault in any sensor and its actual value goes out of specified range, the engine light is turned on and a fault code related to that particular sensor is stored in the engine control unit.

After the technicians perform the Xentry guided test, the faulty sensor is replaced to restore the vehicle to fault-free cognition.

  • Leak in the charger air system

Mercedes Benz engines in the Sprinter are turbocharged, compressed air is cooled in the charge air intercooler and reaches the intake manifold through the intercooler hoses. 

If there is a leak in the charge air system due to a cut in the intercooler hose or leaking intercooler, the air mass measured by the air mass sensor located at the air filter will deviate hugely from the actual air mass going in the engine. The percentage of oxygen measured by the oxygen sensor will be outside the normal operating range.

The fault codes like P0101 can be present in the fault memory, after rectifying the leak in the charge air system, the air mass drift compensation is reset back to 0 and fault codes are erased from the control unit.

Conclusion

As the engine malfunction light can represent a fault in many different systems, it is not recommended to continue using the vehicle without consulting the authorised workshop. All the Mercedes Benz authorised workshops are equipped with the latest Mercedes Benz diagnosis tools and can rectify the engine light malfunction faster than other luxury brands like BMW and Audi.

FAQs: What is an engine light malfunction in a Mercedes Benz Sprinter?

Can I Drive My Mercedes with the engine check light on?

It is possible to drive the Mercedes with the engine check light on but depending on the cause of the engine light, the Vehicle can behave differently. The engine performance will be limited and the car can go into limp home mode. Therefore it is important not to drive a Mercedes Benz with the engine check light on as the fault can cause additional damage.

What does an engine check light mean in a Mercedes?

The engine check light means there is a current fault code in the fault memory of the engine control unit. The engine control unit constantly monitors the exhaust parameters like lambda and temperature. If any sensor detects a major deviation from the set parameter, the engine light is activated and the fault code is stored in the DTC memory.

What is the most common reason for an engine check light?

The most common reason for the engine check light is a bad air mass sensor or even an outside air temperature sensor. Mercedes Benz engines have many pressure and temperature sensors. If there is a loose contact in the electrical lines between the control unit and the sensors then the engine check light is on.

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