Ron Rendezvous 2005 wrote:
I have a 2005 Buick
Rendezvous with 190,000 miles. Yesterday, speedometer went to 0 then below. It did seem to respond slightly but incorrectly to speed changes. Turn off and restart didn't fix. Pulled and restored wrong fuse. Then I pulled fuse 41 in passenger fuse panel for the instrument panel. Start car with no panel life. Shut off car, replace fuse. When fuse replaced, no key in ignition, a "card shuffling" noise occured in dash. Started car and drove and all dash indications good, speedometer accurate. By the way, the only bad indication so far was speedometer. Transmission shift and odometer had always been fine. Cheers :D :D Saved maybe $500.
Drive today good for ~hour. Filled up with gas, guage good. About 1 hour later fuel gauge went from full to about 1/8 tank. Speedometer SEEMED to be working. Shut off car restart no change. Little later on highway, speedometer deffinitely bad and stayed bad.
Shut off car for ~1 hour, start car...Surprise gas guage defintly fixed itself but not speedometer. Pulled fuse, start car no dash. shut off car replace fuse same shuffle noise. Look at dash before key in ignition and speedometer has moved from negative to 0, fixing itself. Started, gas guage accurate, drove all guages good... FOR NOW. I see online that it MAY be the Body Control Module (BCM). Lots of money and some say the problem reappeared. Please help this Poor man. Thanks
The reason you have read on some of those other automotive forums that people replaced the BCM and some still have the problem, is that the BCM has nothing to do with the speedometer or fuel gauge on this vehicle. The speedometer and fuel gauge are sent data via the serial data line from the Powertrain Control Module(PCM) not the BCM. That is the problem with forums full of people just telling about their repair tries that are not GM vehicle tech's. I would bet most of those other posts where people say they replaced the BCM, 1/2 of them wrote back that it did not fix the problem, the other 1/2 just did not bother to update their post and tell that the SUV is still not fixed.
With the removing of the fuse and re-installing, you are resetting the internal memory of the dash (IPC). My best guess would be a faulty dash cluster. Although we have problems with the fuel level sensor
in the tank as well, but having the speedo problem at the same time would suggest both are related- the two things in common are the PCM or the IPC. But also the serial data line, which is basically just a wire the modules use to communicate with each other. You really need have the truck hooked up with a scanner to view live fuel level sensor
and vehicle speed data to help diagnose the problem. Throwing parts at it will get very expensive, as you have read elsewhere.