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RobertFini · #12 07-26-2006, 02:49 AM

So, I finally got the car back from my local dealer, after nearly two GLORIOUS weeks with that Mars Red C280 4MATIC. What a sweet little piece of tail that thing is! It's got me seriously thinking of giving up on the C36 and going for a new C350 Sport Sedan in Mars Red with the six-speed manual transmission. I'd get the split-folding rear seats and the roof rack for cargo capacity, and of course include heated seats like all real cars must have. It's only two-tenths of a second slower to 60 than my C36, and boy-oh-boy is it SEXY! Mmmmm....

Anyway, they had three different gizmos hooked up to various electronic orifices on my car for more than a week, and couldn't get the problem to repeat itself so they could document and measure it. I gave my permission for the shop foreman to take the car home for the weekend, and he apparently beat the living crap out of it until the problem resurfaced (I can't fault him because that's what I told the Assistant Service Manager he'd have to do). FINALLY!

So here it is....

The cover plate on the false floor where the transmission control module lives had been chafing against the feed wire from the vehicle speed sensor long enough to cut through the insulation. Intermittent contact between the cable's inner conductor and the grounded floor plate caused the control module to read a faulty sensor, which apparently is an indication for a failed conductor plate. I just picked the car up tonight and the problem has yet to resurface after probably 50 miles of driving, so we do not yet have definitive proof that the problem is resolved.

Supposing it is gone and we're "good as new," the troubleshooting process for such a complicated electronic system that was used by BOTH factory-authorized dealers seems to me to be suspect. Yes, I'll admit that an intermittently shorting conductor is a real ***** to diagnose and locate, but I have always begun at the sensor and worked my way back to the processor whenever trying to debug my own designs and creations. And I won't even mention the fact that this control module was installed about a year ago by my local dealer, whose technicians didn't seem to pay particular attention to the routing of the cable harness after they were finished with their work.

Any and all comments are most welcome at this point, especially in regards to making the jump from the C36 to the C350. Thank you all for your interest and I appreciate your attention.

Best Regards,
Rob