This past week we fixed fault code P1402 on a Mercedes-Benz with a diesel engine. We wanted to share the solution because this problem seems to affect a lot of Mercedes-Benz Sprinter, E, GL, ML, R Class models with diesel engines.
This problem is often caused by a faulty Pressure Differential Sensor DPS (Part Number A6429050100 ) for the Diesel Particulate Filter (DPF). Replacing the pressure differential sensor takes approximatly 30 minutes.
This is a list of the symptoms that the owner was experiencing.
After diagnosing the car with a Professional OBD-II scanner we found the following code.
In addition to the check engine light, you will notice that your Mercedes struggles to accelerate. This is because the boost is turned off, and you are driving without the help of the turbo. In addition, the ECU restricts maximum RPMs. The car still changes gears, but it is very slow to accelerate which can be very dangerous. While similar, this is not the same as the limp home mode where the vehicle gets stuck in second gear.
Replacing the DPF sensor will fix the P1402 and slow acceleration problem in most cases. The DPF sensor is located near the particle filter right above the transfer case. It can be accessed from under the vehicle.
Drive the front (or rear) of the vehicle up on ramps. It doesn't matter if you get the front or back up on ramps. The sensor is located approximately in the middle of the vehicle. Secure the back wheel and place jack stands to support the vehicle.
Looking from the driver side you will see the DPF sensor.
Note that the connector for our new sensor was not exactly the same as the old connector. We had to remove the old connector (from the old sensor) and install it on the new sensor. Once we switched connectors, we were able to plug in the DPF sensor connector into the wire harness with no issues.
Once the new sensor is installed, clear the codes and test drive the vehicle. Engine power should be back to normal range. If the problem persists, check for a damaged wiring harness and also check the connector.
This problem affects multiple Mercedes-Benz vehicles with a diesel engine. Below is a list of possible applications.
Check with your Mercedes dealer to verify part number.