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Old 08-06-2003, 11:43 PM
RProsser RProsser is offline
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Join Date: Aug 2003
Posts: 48
Ready to go on vacation and the &$#% check engine light comes on!

Hey all. We are about to head for Lake Powell for some water skiing and the damn check engine light has come on our '97 C280 (silver/dark leather w/65K mi). Hoping you can shed some light.

I suspect the light means the mass airflow sensor or one of the (rear?) 02 sensor, but would like to confirm first. The nearest dealer wants $100+ to read the codes AND I have to drop it off. I called a few of my local San Diego County Peb Boy shops. Only a few do it, and those have to make an appointment because the tech that does it is not always in. Oh, and it'll be $85 bucks. Still no way to get a fast diagnosis. I can't wait three days.

FYI: For good measure, I checked the gas cap, the throttle position sensor and then pulled the MAS and sprayed some carb cleaner on the hot wire, then I climbed under the car to inspect the two 02 sensors. Everything is intact. I fired up the car, and took it out for a romp. It runs great! In fact, it hauls ass for a 2.8! The light is still on, but it idles and shifts fine and I can't find a damn thing wrong with it.

So what's this about an "onboard diagnostics" -- is there some kind of DIY utility on the car that I don't know about? I know tons about Porsche, but not near enough about MBZ. Guess that's about to change.

Deductive reasoning: all the parts guys I spoke to today say the MAS is a regular sales item. It's a 3-minute replacement part. That's the upside. The downside is that the friggin' thing costs $250! The same parts people I polled do not stock the front 02 sensor -- only the rear, so that tells me the fronts do not go out often. The upside is that the normally stocked 02 sensor costs $125. The downside is that it looks like a total pain in the @$$ to remove! It's in the middle of the "Y" at the back of the catalytic converter. How the heck are you supposed to get a wrench on THAT!?

Ready for a family vacation, so any ideas would be very much appreciated!
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