Speedometer Odometer issue
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Don’t know the 90 that well but if it is like the later vetts;
Look for any codes that might relate to the vehicle speed sensor in the transmission not working.
Bad ECM, or bad connection to ECM from vehicle speed sensor.
Look for a bad connection in a connector on the dash unit and CCM (BCM).
Problem could be a bad solder connection in the dash unit.
Look for any codes that might relate to the vehicle speed sensor in the transmission not working.
Bad ECM, or bad connection to ECM from vehicle speed sensor.
Look for a bad connection in a connector on the dash unit and CCM (BCM).
Problem could be a bad solder connection in the dash unit.
Last edited by pcolt94; Jul 12, 2012 at 09:24 AM.
Instructor
Joined: Feb 2012
Posts: 145
Likes: 0
From: Brandon MS
What year? My 93 speedometer doesn't work until I've been driving about 20 minutes, then it works. Think I have it tracked down to the plastic gears on the VSS and the plastic drive gear from the transmission. If yours doesn't work at all it could be the wiring between the VSS and the ECM or it could be the VSS itself. There is a diagnostic section on this in the service manual, but the people that will help you here need more info about your car. Year, auto or manual to get started diagnosing your problem.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
What year? My 93 speedometer doesn't work until I've been driving about 20 minutes, then it works. Think I have it tracked down to the plastic gears on the VSS and the plastic drive gear from the transmission. If yours doesn't work at all it could be the wiring between the VSS and the ECM or it could be the VSS itself. There is a diagnostic section on this in the service manual, but the people that will help you here need more info about your car. Year, auto or manual to get started diagnosing your problem.
Its a 1990.
Team Owner
Joined: Sep 2003
Posts: 25,366
Likes: 2,733
You've no CEL and error codes?
If your car is a C68 auto/AC you can check speed on the digital display using I believe parameter 7, if you've got speed displayed there then it's an IP/Cluster issue I'd think. If you've no display there then you could start at the VSS and move on from there. This part is the easy check.
You could actually remove the VSS to physically check the condition of the drive and driven gears, I would think you could remove the driven gear from the VSS and spin the shaft of the VSS with a drill to confirm operation of the VSS. I'd check the connector also for the VSS, clean it well. If you've got speed on the cluster then the VSS is fine and you likely should have found a problem with the drive/driven condition or you've maybe disturbed the wires in the connector and it's begun working again.
Have you recently done any transmission work or any under-car maintenance?
If your car is a C68 auto/AC you can check speed on the digital display using I believe parameter 7, if you've got speed displayed there then it's an IP/Cluster issue I'd think. If you've no display there then you could start at the VSS and move on from there. This part is the easy check.
You could actually remove the VSS to physically check the condition of the drive and driven gears, I would think you could remove the driven gear from the VSS and spin the shaft of the VSS with a drill to confirm operation of the VSS. I'd check the connector also for the VSS, clean it well. If you've got speed on the cluster then the VSS is fine and you likely should have found a problem with the drive/driven condition or you've maybe disturbed the wires in the connector and it's begun working again.
Have you recently done any transmission work or any under-car maintenance?
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Team Owner
Joined: Sep 2003
Posts: 25,366
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CEL - Check Engine Light
I guess it's time to get under the car. It seems the likely place to start. Have you done an ECM or CCM replacement recently or had reasons to "mess with" the connectors at the ECM or CCM. The diagnostic tree for VSS I believe actually starts with ECM/CCM connections etc but if it's not a nuisance to get to the VSS I wouldn't think it unusual to check for a bad/loose connector, physical damage to the VSS and gears!
-Good Luck
You might want to get into the instrument cluster diagnostics and check for codes for the CCM etc. It's certainly easy enough and maybe a good start rather than doing the "under car stuff"!! There's I believe also a MPH parameter in that also!
Last edited by WVZR-1; Jul 12, 2012 at 05:14 PM.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Before you pull the Vehicle speed sensor out, go to Chevy and buy a new O ring for it. If you plug it back in with the old o ring, it will develop a leak.
Best $1.50 you will spend. Keeps the mess to just a couple drops on your fingers.
Best $1.50 you will spend. Keeps the mess to just a couple drops on your fingers.
Thread Starter
Cruising
Joined: May 2012
Posts: 11
Likes: 0
Replaced the ecm last week but the problem was there before. Ecm and O2 sensor have solved the running rich problems I was having. Now working on the next problem this. I am in middle of Iowa not a lot of Corvette mechanics.
Team Owner
Joined: Sep 2003
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Do the cluster/ip diagnostics and see what you find there and then move under the car. Checking the physical condition of the VSS and the gears costs you nothing but time and the cost of the seal required, that was a good catch by "coupe guy 2001"!