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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53302
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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98 ML320: Check engine light..OBD2 codes p300, P0304..MAF..O2 sensor

Customer Question

98 ML320 w/ 130k. Check engine light with OBD2 codes P0300, P0304, P0305, P0306. suspect MAF or O2 sensor. Drives fine until accelerate too quickly, then pulls codes. Can reset codes and it's fine until same situation occurs again. Seems like truck is going into limp mode. Have cleaned MAF with no change, but hope there is a way to identify more specifically which sensor is responsible or which of the 4 oxygen sensors would be most likely. Had been great until 2 days ago and started all of a sudden. Would think o2 sensor or MAF would pull different codes in addition to random misfires.
Submitted: 5 years ago.
Category: Mercedes
Expert:  Marty replied 5 years ago.

eurotec :

Hi, this sounds more like a restricted catalytic converter for cylinders 4, 5 and 6.

eurotec :

I'd perform a converter back pressure test or just loosen the converter and road test the car and see if that solves the problem.

eurotec :

If it were a maf or O2 sensor you would have fuel trim codes or oxygen sensor codes.

eurotec :

Your symptoms are typical of a plugged converter.

eurotec :

Let me know if you have any questions or if you need more help with it.

eurotec :

And please remember to click Accept so I receive credit for my help.

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