Speedometer too fast
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 3,754
Likes: 89
From: arvada co
Speedometer too fast
My speedo flipped out the other day. The speed now reads too fast.
Crawling across a parking lot it reads 12 MPH; at about 45 actual speed it reads 75 MPH. The speed delta is consistent, it’s not jumping around, like reading 0 when I am driving. The cruise control works, it maintains speed that is displayed. Speedo does the same reading if it is cold or hot.
Can I rule out the VSS on this? Does the VSS simply change gear rotation to RPM signal? My guess is that the VSS sends a RPM signal to a chip somewhere that does the calculation RPM * X, Y, or Z (based on current trans gear) = MPH.
Car is stock 1993 with automatic.
Any help is appreciated.
Crawling across a parking lot it reads 12 MPH; at about 45 actual speed it reads 75 MPH. The speed delta is consistent, it’s not jumping around, like reading 0 when I am driving. The cruise control works, it maintains speed that is displayed. Speedo does the same reading if it is cold or hot.
Can I rule out the VSS on this? Does the VSS simply change gear rotation to RPM signal? My guess is that the VSS sends a RPM signal to a chip somewhere that does the calculation RPM * X, Y, or Z (based on current trans gear) = MPH.
Car is stock 1993 with automatic.
Any help is appreciated.
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 3,754
Likes: 89
From: arvada co
ENG / MET button.... DOPH!
I'll let you know how that works out.
Last edited by colo63sw; Jul 23, 2019 at 02:44 PM.
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
Look at it this way. Aren't you glad that all you had to do is push a button rather than go digging into the trans? This was the best kind of problem to have.
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 3,754
Likes: 89
From: arvada co
