94 ParkAveUltra


About a week ago,my speedometer/odometerstarted working intermittently. They have since stopped working all together. When they were working though, my engine would run normally andidle speed would be relatively low. Now that they aren't working, idle speed is around 2200RPM and compared to earlier, the car jumps like a jackrabbit when I take my foot off the brake at a stop light.


When I plug in the OBDII, it won't connect to the ECM. So I replaced the Throttle Position Sensor and the Speed Sensor that's plugged into the tranny. Still nothing. I'm at a loss at this point.


It sounds like I have a vacuum leak as well but I don't know where it's coming from and am not sure if that's part of the problem or not. Any help would be appreciated.

OBD II began in 1996. Some earlier vehicles had OBD II type connectors, but were not actually OBD II compatible. I believe that adaptors are available.Edited by: MrBSS

yeah, you're right, I misspoke. I just meant to say that when I plugged the Snap-On scanner in, it wouldn't communicate with the car. Any ideas though?

I think your on the right track to get the OBDI Codes read off that OBDII connector...it requires a special cable adapter for most readers for that year.

If you don't get it to read with the proper adapter cable, you may have a PCM problem causing all the symptoms of not readable codes and idle too high and speedometer.

If you get the first codes read, it may also help to start by resetting the PCM by disconnecting the battery for 10 seconds . Run it for a bit to see if there is any improvement. Just for a hopeful try.

Vacuum leak would be considerable to get 2200 rpm.

I personally had a PCM failure. The Cruise Control would disengage after random periods of operating.

I think the speedometer works from information directly from the PCM.



Edited by: bassasasin

PCM, that was it. Car runs like a dream again. Thanks.