Mercedes-Benz vehicles such as GL, ML, R, Sprinter equipped with diesel engines (including Bluetec) may trigger the check engine light wich fault codes such as P0544, P0546, P2201 or P2031 pointing to a bad Exhaust Gas Temperature Sensor Circuit. If data is read from the sensor you may get an error sensor out of range and a code for B19, B19/9, B19/11 also known as TWC temperature sensor, error code 249 f . Even if you clear the code, it usually returns after a few days. In a few cases, the vehicle may go into limp mode when this fault code is triggered.
The sensor may work as designed when it cools down but once the engine and catalytic converter warms up the sensor does not provide the correct temperature reading. To diagnose the performance of the sensor, allow the engine to warm up to operating temperature. The temperature from these sensors should be in the 450 to 700 degree F range.
This problem is often caused by a defective exhaust temperature sensor (also known as B19, B19/9, sensor which may have various part numbers such as A005 153 40 28 or A007 153 74 28, A 005-153-45-28, A 007-153-63-28 . Call your Mercedes-Benz dealer and provide the VIN to verify the part number. Typical cost to change one of the sensors ranges from $300 to $480. You Mercedes-Benz can have up to four sensors. Built upon the sensor can hinder its performance. The sensor can be replaced or in some cases cleaning the sensor can fix this problem.
Solution 1 - Replace Sensor
To fix this problem you will need to replace the defective sensor.
- Raise up the car at the front. Use jack stand or ramps.
- Remove the soundproof shield to access the catalytic converter and exhaust pipes.
- Locate the exhaust temperature sensor. There are two to three exhaust temperature sensors on Mercedes diesel models and Dodge Sprinters. Which sensor needs to be replaced depends on the fault code. Mercedes Exhaust Temperature Sensor
- Loosen the 17mm nut and pull it away from the sensor.
A stubby 17mm wrench makes removing the sensor much easier.
- Remove the sensor from the exhaust, DPF or catalytic converter. Note that the sensor tip is long. Do not bend the sensor part.
- Remove any clips that hold the wire in place. In this case, a zip tie was used to hold the wire. A long screwdriver was used to cut the zip tie due to space constraints.
- Unplug the electrical connector.
- Install a new exhaust temperature sensor in reverse order.
Solution 2 - Cleaning Mercedes Exhaust Temperature Sensor
It is possible to remove the sensor and clean it. You will need to use Sensor Safe Spray Cleaner to remove any built upon the sensor element. Blow air on the sensor element to clean it.
Cleaning the sensor may not always work. There is a high chance that the problem will return in a few months.
Check electrical connector
If you clean the sensor or replace it but the code returns, make sure that the electrical connector is not saturated with oil or the wire harness is not damaged.