Speedometer will not return to zero?

Hi,

If both are doing the same thing at the same time, it may be the cluster or a module related issue. Have you checked the wiring connection at the cluster? If not, check that first,

If the connector is in good condition, I recommend scanning the can-bus system. CAN stands for controller area network. Basically, the different modules are tied together via a few wires. This type of scan will retrieve codes regardless of the module storing them.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Let me know if that is something you have done or if you can have it done.

Next, I found an interesting technical service bulletin I would like you to review. I attached it below. I don't work for a GM dealership, so I'm not familiar with the issues. However, the bulletin indicates an updated warranty and policy related to certain electronics. The instrument cluster is on the list.

Take a look through the pics below. It may be worthwhile contacting a GMC dealer to see what they say.

Let me know.

Take care,

Joe

See pics below.