Hey guys, 99 zr2, my speedometer bounces a bit, it doesn't seem to do it all the time but is a little annoying when it does. I have noticed it seems to do it more when I am decelerating, it will kind of stick and then drop down 10mph or so at a time instead of gradually dropping with my speed. It doesn't seem to cause any issues with anything else, however I would like to fix it before it becomes a larger issue. What can I look at here?

 

If that's the only problem you're having with the cluster, and no DTC's are in the BCM, (body control module) (BCM DTC's will not turn on the SES light) it could be a sticky stepper motor for the speedo. Not real common on S&T body, but GM had a ton of problems with steppers on full size C&K Silverado, Avalanche, etc. The motor can be replaced, but it involves complete disassembly of the cluster and circuit board, then de-solder the old motor and solder in a new one. The motors are cheap on Ebay etc, (under$5).

Some scan tools can access the VSS, (vehicle speed sensor) on the transmission to see if it's providing a smooth signal to the BCM. Most of the high end scan tools can access the BCM and command a "needle sweep" of all gages. It might not be a bad idea to pay a shop to perform the needle sweep and check the VSS output before going any further.

 

Ok, thanks Captain, I will look into that abit. Do you know if there is anything else that can come from this if I cant get that done right away? I don't get a CEL, however dont know if there are any BCM DTC's, I dont notice any other issues with the truck at all tho. Is there something else I should be looking for, maybe this is part of a bigger issue that I am unaware of? Thanks again

 

Shouldn't cause any other problems. Using the scan tool for the needle sweep tells you instantly if the BCM is capable of controlling the speedo correctly, and if the stepper motor is working smoothly. If the transmission shifts properly and the ABS light doesn't come on, the VSS is most likely ok.

 

Ok, thanks again. The transmission shifts normally albeit a bit soft for my liking, but normal, and no abs light. When I get a chance I will have a needle sweep done.

 

im having the same problem with mine i hooked my scanner to it and idling when it moves the needle it wil ltell my scan tool im goin 5-10 mph. on computer and on cluster.... what gives? i can rev the engine and it will sometimes move while in park reving.