Hello. I have a buddy that drives a 1991 m30. recently, he came out and noticed the speedo was pinned all the way up. Iam not familiar with these cars and can find very little info about them. Iam a heavy truck mechanic so i am familiar with a few different set ups. I was hoping to get an opinion on the matter before I go look at the car tomorrow. In my mind the speed sensor is out because in most vehicles the sensor is a magnet/coil and makes a/c voltage to make the gauge go up. I also read that on this model the a/c signal goes directly to the speedo head before the ecm, kinda backwards from what i normally see. Does this speedometer head unplug from the gauge cluster? Is this a common problem on this car? do i need to bring any special tools with me for disassembly? Any help would be greatly appreciated. Thanks a bunch.