Odometer runs backwards sometimes


#1

I have a 87 Pontiac Fiero.



My problem is my odometer milage did not seem to be keeping up with my trip odometer.

I started watching and yep every now and then the odometer will stop and then start going backwards for about 2 miles and then start running normal again.

On a 900 trip meter reading I ended up getting about 750 miles on the odometer.

Everyone I ask about this says it is impossible but it does happen.

Do you have any idea what mey be wrong?


#2

At some point, GM switched from a mechanical speedo head to an electronic one. It’s entirely possible with the electronic one. If your speedometer and trip odo work, the problem is probably the little motor that drives the odometer (not the vehicle speed sensor). It would be… not so fun to buy one from the dealer. I don’t know what the procedure is for replacing an odometer and declaring it legally with the DMV… probably a question for the DMV. But anyway, you need to replace the odometer (probably easiest to just replace the whole speedo assembly.)