If it is the same problem that appeared on my '04, it is going to be the instrument cluster. The speedometer is part of it and couldn't be changed independently. Mine started bouncing some when I would first start it up, then start working normal. I ignored that for a while. Then it got to where it would not move at all till I had driven some , then it would start working right. It finally got where it wouldn't move at all or just peg out. I had the cluster changed and that fixed it.
A 1991 dodge dynasty speedometer bouncing could be a sticking speedometer cable, or a bad drive gear. Check the cable first, and lubricate it to see if the problem stops.
check the fuse, the speedometer does not run off of a fuse
Nope, bet it was the other way around... Your speedometer stopped working and your check engine light came on. A broken speedometer (don't know what car so I can't pinpoint it) will cause a whole bunch of codes.
If the speedometer stopped working on a 1990 Cadillac Seville, it could be the fuse or an electrical problem. First check the fuse and if the fuse is good, check with a mechanic.
check your speedometer sensor located back left of engine bay on top of the transmission
If the Park Ave is a year that uses a speedometer cable, check that the drive gear for the cable is working. Check the cable to insure that it is not broken of stuck, then check the speedometer itself. These steps will let you know what is broken so that you can fix it.
the speedometer on my 97 toyota camary stopped working and the check engine light came on why
If the speedometer breaks, it effects the odometer. Check the speedometer cable it may be broken, even under the insulation.
Check the fuses
Have your mechanic check the speedometer cable connections. They no longer use a cable. It is electronic. If the speedometer is not working but the odometer is, the problem is in the dash cluster. If both the speedometer and odometer are not working, the speed sensor in the transmission may be at fault.
check speedometer cable for possible disconnection; it comes out of firewall and goes to transmission
I think you need a speed sensor