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Ask Michael Warfield Your Own Question
Michael Warfield
Michael Warfield, Factory Mercedes-Benz Technician
Category: Mercedes
Satisfied Customers: 3131
Experience:  Mercedes-Benz Master Certified technician
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When M320 cdi start the engine i can drive with no problem

Customer Question

when M320 cdi start the engine i can drive with no problem unlimited miles when i stop and start again on hot engine the mersedez is going to limp mode. i have to wait the engine to cool down and start again so there is no problem
Submitted: 1 year ago.
Category: Mercedes
Expert:  Michael Warfield replied 1 year ago.

Did you clean out the EGR pipe in front of the engine? It will set an EGR fault code because it clogs the flow. I'll try and find a picture.

Customer: replied 1 year ago.
Expert:  Michael Warfield replied 1 year ago.

The pipe goes from the bottom of the throttle body to the EGR oil separator, it is the large silver "J" shaped pipe in the bottom center of the picture.

Expert:  Michael Warfield replied 1 year ago.

So the pipe was clean? Did it have a lot of carbon?

Customer: replied 1 year ago.
No, the EGR was clean too, but i decided to change it too.
Customer: replied 1 year ago.
Anything else???
Customer: replied 1 year ago.
I don't understand why paid 31 dollars???
Expert:  Michael Warfield replied 1 year ago.

Is that the only fault code you have? Have you tried getting the engine scanned with a more advanced scanner? It should tell you a more specific fault code such as EGR positioned fault or poor flow.

Expert:  Michael Warfield replied 1 year ago.

Do you know if the EGR cooler below the intake manifolds is clear as well?

Customer: replied 1 year ago.
No, I only have this code
Customer: replied 1 year ago.
everything is clean
Expert:  Michael Warfield replied 1 year ago.

Ok, is your scanner capable of reading transmission fault codes or only OBD engine faults?

Expert:  Michael Warfield replied 1 year ago.

The 1402 fault code is a generic OBD fault. The actual engine and transmission computers will store specific manufacture fault codes that will be more specific to the problem. You could have a DPF/exhaust problem but it would be hard to tell with a generic fault code.

Expert:  Michael Warfield replied 1 year ago.

The mercedes specific code might be for the Diesel Particulate Filter pressure differential sensor. This is how the computer determines how much flow in the DPF sensor but I know it can trigger a generic P1402 EGR fault.

Expert:  Michael Warfield replied 1 year ago.

I would suggest replacing the DPF sensor if you a more comprehensive engine scan of the fault codes is not available.

Customer: replied 1 year ago.
I will scan tomorrow with more advanced scanner but i agree with you and the change of the differential pressure sensor is my next move
Expert:  Michael Warfield replied 1 year ago.

Ok, let me know what you find.