Mercedes DPF Exhaust Pressure Sensor Problem P1402 Code 2078

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.

Mercedes Dodge Sprinter DPF Exhaust Pressure Sensor OEM # A6429050100

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. 

Symptoms

  • Check Engine Light on
  • Reduced engine power
  • Vehicle slow to accelerate / Limp Mode
  • Fault Code P1402

After diagnosing the car with a Professional OBD-II scanner we found the following code. 

  • Code 2078-008: Check Component B28/8 (Pressure differential sensor DPF). Plausibility error with ignition on. 

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. 

How to replace Mercedes DPF sensor

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. 

What you will need

Instructions

  1. Slide under the car and locate the DPF sensor above the rear driveshaft. Mercedes Dodge Sprinter DPF Exhaust Pressure Sensor location

    Looking from the driver side you will see the DPF sensor. 

    mercedes dpf pdf sensor
  2. Remove the 10mm bolt from the sensor. replacing dpf sensor

     

  3. Pull down the DPF sensor to remove hoses and connector. mercedes particulat exhaust sensor

     

  4. Remove the clic-r clamps from the two hoses. Pay attention to the hoses. One is larger than the other. Remove hoses from DPF sensor.disconnect dpf sensor mercedes r320 ml320 sprinter e320

     

  5. Press both sides to unplug the electrical connector.disconnect connector from dpf sensor

     

  6. Install hoses in the same position. Use new hose clamps.installed new dpf sensor mercedes 
  7. Connect the electrical connector. 
  8. Install the DPF sensor on the car and tighten the 10mm nut. 

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. 

Applicable Vehicles

This problem affects multiple Mercedes-Benz vehicles with a diesel engine. Below is a list of possible applications. 

  • C-CLASS     2001-2007
  • CLK     2002-2009
  • CLS    Diesel
  • E-CLASS     2006 -- Current
  • G-CLASS  
  • GL-CLASS     
  • GLK-CLASS   
  • M-CLASS     2005 -- Current
  • R-CLASS     2006 -- 2012
  • S-CLASS     2005 -- Current
  • SPRINTER   2007 -- Current
  • VIANO     2003 -- Current
  • VITO / MIXTO Box     2003 -- Current
  • VITO Bus     2003 -- Current
  • SMART
  • FORTWO 2007 -- Current

Related Part Numbers

Check with your Mercedes dealer to verify part number. 

  • A6429050100 
  • 642 905 01 00
  • 006 153 49 28
  •  006 153 95 28
  • 007 153 61 28
  • A 006 153 49 28
  • A 006 153 95 28
  • A 007 153 61 28
  • A 642 905 01 00
  • 550627 16100 43587
  •  84319 6PP009409001 0281002924

Comments

Hi.

What do you mean switchin' connector?

I noticed while doin it, there is a slight problem, like the new aftermarket sensor doesn't click like the original...

I changed it, but scanner still shows me the same error and have the same accelerating problems...

Thx

The old connector at the end of the wire harness was not the same as the old one. If you look carefully you can disasemble the connector for both the new and old sensor that you removed and swap them. This will allow you connect the new sensor to the connector (plug) where you disconnect the sensor. If the connector does not click, there is no contact made, so you are going to get the same fault code.

Ideally you have the sensor with a connector that will fit perfectly. We didn't but once the connector (plug) was switched, everything worked fine. No more codes.

Thx for reply. I didn't got or see a new harness-connector (CLS 320 cdi)

I feel that the new Herth+Buss sensor doesn't work like it should. Still have the same error. :(

I'm gonna go with OEM Mercedes now, hoping for the best. :) And the connector should fit. It better. :)

 

 

Update;

got Merc sensor A 642 90 501 00,

probl solved, car pulls over 3000 rpm, none problems with the old harness-connector.

Both error subcodes for P1400 (P2270 and P2078) are gone.

Cheers

 

Joey L, 2019-05-06

I've had this issue on a 2017 CLS 250d fixed by a Mercedes dealer (its in warranty) twice now, and the issue has just popped up again for the third time. Everytime its fixed, the issue arises again in 2 - 3 months.

Daniel_Arkansas, 2019-05-24

My 2008 I just bought last weekend is doing this (oddly enough a day after it was serviced).

I got the P1402 but after clearing with my bluedriver 1402 disappeared and now I have p1400 instead....

Doing a dpf delete and tuning this weekend and I'm wondering if it makes any difference after having the car tuned if this pressure sensor is out.

The ECU is no longer going to care about the pressure anyhow if i understand it right?

Daniel_Arkansas, 2019-05-24

Wow! It worked! Took a chance and bought the recommended part at the stealership. Well over 100 dollars, but I wanted the OEM part.

Once I got to the old one, noticed it had been previously changed for an aftermarket one.

My MB wouldn't go past 3000 RPM. Wasn't in full limp mode, but next to it.

Reved past 3000 right away after installing.

Still had a low reading on the pre dpf pressure which probably points towards the dpf being closed to clogged.

Anyhow, just sent off my ECU dump to greendieselengineering.com. As soon as I get this file back I'll be deleting the dpf and disengaging the EGR and swirl flaps ;-)

THANK YOU!!!

(The local Mercedes mechanic was talking about all kinds of things they thought they'd have to change... Most likely saved alot because of this page!!!!

Moses, 2019-06-14

Hi,my 2008 CDI E320 has this error “Check power supply of component B28/8(Pressure Differential Sensor (DPF)) open circuit or short to ground in the signal line” is this the same or it’s something different, any idea what this means it started after DPF regeneration done at the garage.

Lorant Ersek, 2019-07-26

too reset DPF B28/8 senzor i need Star Diagnosis scantool?

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