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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53904
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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The cel on a 98 c230 repeatedly comes on with a p0170 code.

Customer Question

The cel on a 98 c230 repeatedly comes on with a p0170 code. The maf has been replaced twice, the o2 sensors have been replaced, and numerous vacuum hoses have been replaced. What other items could cause the cel to come on.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is***** can also be caused by vacuum leaks or low fuel pressure or a faulty mass air flow sensor. Ideally you should have the intake system smoke tested for vacuum leakage. Small leaks can be difficult to locate without a smoke machine. A faulty brake booster could also cause the problem. Fuel pressure should be tested to be sure it is between 55-60 psi. If you are not using genuine Mercedes mass air flow senors you could be getting defective sensors.

Let me know if you have any questions.


Customer: replied 1 year ago.
Fuel pressure has been checked and is good. Genuine Mercedes mass air flow sensors. Numerous vacuum have been replaced, but I do not remember how many. I do not believe a smoke machine has been used. The brake booster is a new one. Any other thoughts?
Expert:  Marty replied 1 year ago.

You should be looking at the fuel trim values on the scan tool to get a better idea as to the mixture problem. More than likely they have missed an intake leak. I'd suggest smoke testing the intake. You could also block off the brake booster and see if the trim values change.