So recently the speedometer is saying about 10mph more than it is actually going. the odd thing is if I plug in something for OBD2 for direct reading, that mph is correct, just the cluster *ępeedometer is off. Everything else on the dash is correct, except the rpm also, that is showing a couple hundred faster. my main concern is the Speedometer. cruise control works, based on actual speed, not speedometer. meaning to activate you must be going I believe a minimum of 25. if speedometer says 30 it won't turn on, but when the actual speed is 25 it will.

I replaced the VSS, that didn't fix anything. I took the cluster apart, swapped the speedometer motor with the fuel gauge motor which is exactly the same (not every of the gauge motors are the same with one another).

that didn't do anything, I tried like making the needle 10mph slower. still no progress.

the weird thing is I used to be able to plug in my cheap ELM327 Bluetooth adapter but that doesn't connect to my car anymore. I mean the thing works in other cars, but not mine. same thing with a HUD speedometer, won't connect through the obd2. but I can get an actual obd2 scanner to hook up.

So what can the problem be and how can I fix it? I do have the airbag unplugged for the time being to fix something unrelated. would this be the cause?.
I have no idea what else it can be.

​​​​​1999 Pontiac Bonneville SLE 3800 Series II 4T65-E

So recently the speedometer is saying about 10mph more than it is actually going. the odd thing is if I plug in something for OBD2 for direct reading, that mph is correct, just the cluster *ępeedometer is off. Everything else on the dash is correct, except the rpm also, that is showing a couple hundred faster. my main concern is the Speedometer. cruise control works, based on actual speed, not speedometer. meaning to activate you must be going I believe a minimum of 25. if speedometer says 30 it won't turn on, but when the actual speed is 25 it will.

I replaced the VSS, that didn't fix anything. I took the cluster apart, swapped the speedometer motor with the fuel gauge motor which is exactly the same (not every of the gauge motors are the same with one another).

that didn't do anything, I tried like making the needle 10mph slower. still no progress.

the weird thing is I used to be able to plug in my cheap ELM327 Bluetooth adapter but that doesn't connect to my car anymore. I mean the thing works in other cars, but not mine. same thing with a HUD speedometer, won't connect through the obd2. but I can get an actual obd2 scanner to hook up.

So what can the problem be and how can I fix it? I do have the airbag unplugged for the time being to fix something unrelated. would this be the cause?.
I have no idea what else it can be.

​​​​​1999 Pontiac Bonneville SLE 3800 Series II 4T65-E

I have the info for that vehicle if you need. The cluster has a logic chip that processes the outputs and it is bad.

One post is enough.

It could be the needle has slipped on the stepper motor shaft.

Merged duplicate threads into the thread created in the "Pontiac" forum.

Please do not start multiple threads for the same issue.

The other thread was: https://www.gmforum.com/1992-1999-91...faster-314249/

If the scan tool was reporting a correct speed, but the cluster wasn't, why would this cause you to replace the VSS?

Cluster is afoul. Replace it.