I have been getting the PO300-PO306 codes which is missfire. Plugas and wires have been replaced. I also get the PO170 & PO173 which is fuel rail. My dealer say MAS is the problem. I dont mind replacing but hate to if i just taking a stab in th dark. Also under accelleration is missed very bad and almost get runover in traffic. I know that if there is substancal missing that the tranny will go into "limp mode" for protection. I have a OBDII scanner and reset the codes and now a new one has popped up...PO715-"Input/Turbine spped sensor A circuit malfunction".

Here's the question:
PO715-Is this transmision related and can the MAS be causing engine to run too lean and causing missfire and irratic transmission shifting? I have 180,000miles and is a 1999 ML320.
help is appreciated before all hair is yanked out!

Diagnosis of Mass air flow sensor is most likely the problem for the fuel trim & misfire codes.

The P0 715 almost always means the printed circuir board in the valve body is defective. The speed sensors are built into that part.

The part 140-270-08-61 lists for $210. & installed price should be around $450.

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