Got a 2004 Chevy Impala with 99K miles. Speedeomter seems to be acting sporadically often. Sometimes, it will shift 10 or 20 mph “faster” than actual speed then, sometimes, it goes to the “maximum” speed on the dial and just stays there with the car on or off. Then a few days later, starts working normal again. Suggestions on what needs to be fixed and how much it should cost?
Someone should test the Vehicle Speed Sensor (VSS), which is attached to the transmission.
Try these two links:
http://www.carcomplaints.com/Chevrolet/Impala/2004/accessories-interior/speedometer_gone_haywire.shtml (reference #118 forward)
These are good links. Its the cluster.
i had the same problem but with the fuel gauge and the temp gauge. i ended up replacing the stepper motors myself. if you know how to solder its easy if you dont dont risk it. i did it all myself and it cost me about 40 bucks vs the 1000 bucks for a new cluster from a dealer
Is your tach (assuming you have one) also going nuts? If so, it could also be a bad power or ground wire to the instrument cluster.
Failing that, a malfunctioning gauge like that can generally be only one of three things: a bad speedometer, a bad sending unit (in this case, the VSS), or a short or break in the wire between the two. I’d probably replace them in that order.
Oh, and there’s also a very narrow possibility that your PCM is malfunctioning, but that’s probably about as unlikely as the wire. 