I bough a new-to-me 2003 duramax one week ago today. I didn't even get home and the dash lit up! It was displayingg "service brake system". the speedo was very bouncy and soon after the engine light went on and it displayed "range shift inhibited". I lost reverse and there was a nasty noise when I put it into drive. Turning the truck off, the restarting seemed to deal with the problem, although the service brake system kept comming back.


Local dealership said it was a faulty ground and charged me $100. (even with the extended bumper to bumper warranty).


7 days later the EXACT same thing happened. Same symptoms, same messages and same codes (P0500-speed sensor malfunction, P0700-Transmission control system malfunction, and P0735-Gear 5 incorrect ratio)


Obviously the dealership was off on their diagnosis, anyone else with this problem, or any ideas of what it could be?


thanks.

My speedo was very bouncy in cold starts, heater, wipers and doom light did not work at times. All due to a faulty ground to one of the battery's side post/cable. I went to my friendly CanadianTire store, bought and replaced the exsisting ground battery cable with a 1 gauge ground cable to the battery's top post. No problem since.

Bad ignition switch can cause these symptoms. How many miles? Still under warranty?

yes, it's still under warranty. In the end it seems that it was a seal in the rear transfer case that was leaking on a sensor which was causing false codes to be thrown and the tranny to go into limp mode.

Thank goodnes the previous owner bought extended warranty.

Did you get your 100 dollars back? If not I would put a stop payment on the card or check if possible.