speedometer problem

[88fan]

Hey there, I just got a 96 GT 5 speed. I've driven it around for about 2 weeks now and all of a sudden the speedometer quit. It will read 0 until you hit probably around 40 then it jumps up to about 80. Seems to read about 40 mph faster than I'm going. If I'm going around 60 with traffic it reads 100mph. As far as I know the car is all stock. The only thing I've done is put new brakes all around and changed the oil & filter. Any help would be greatly appreciated.

Thanks.

 

[GDawg]

Check the vehicle speed sensor left rear of the transmission. There's a grey/black wire that goes to your speedometer.

 

[wmburns]

There is a DTC code P0500 for a VSS sensor failure. Since no MIL, it is possible the VSS sensor in the transmission is good. Note, a bad VSS would cause drivability issues on an automatic transmission. Less likely on manual.

Your post stated the car was stock. Will assume factory rear end gears. Therefore, unlikely someone has attempted to change the VSS gearing (or added a speed cal unit). Again, not a bad idea to do a visual check.

To confirm the VSS sensor we will need to monitor the Car Speed as reported by the PCM. If the PCM has a reasonable value, this points to a problem in the cluster.

If the PCM speed is messed up, this points to a problem in the Vehicle speed Sensor (VSS) located in the transmission tail shaft. Start with a visual inspection. Look for loose connectors, excessive oil, loose wires, or any obvious damage.

Are there any other problems with the cluster? Do all of the other indicators work? Does the odometer work accurately?

For cluster concerns, we first should look at any recent work. Has there been any audio equipment installed/removed? I suspect it occurs frequently that the grounds from the cluster get messed with during an audio install. The ground is around the center console very near the radio. There are two on either side of the center console.

The cluster is not hard to remove. This would allow for inspection of the electrical connectors. Look for dirty/loose wires.

Please update the post with the test results.

Good luck.

 

[GDawg]

Gotta appreciate Mr. Burns....

I have the full blown test procedures but I can't copy and paste them.

 

[88fan]

Thanks for your response. I'll check those things. You asked if any other problems. No just the speedometer. Everything else works fine. You mentioned about audio installation. The guy I got this car from was a dirtball. He spilt soda and stuff over the console and shifter. I don't think he ever cleaned or vacuumed the car. I had the center console out of the car to clean it. I also had the radio out and the cd player out to clean. I had driven the car since I did all of that and it worked fine. Maybe something worked loose. I'll update you when I get time to check it tomorrow.

 

[88fan]

Ok, been driving the car today and now the speedometer is working fine. Don't have a clue what caused it or what fixed it. I didn't do anything. It just started working by itself.