Hi,
Spark plugs wouldn't cause this or the OnStar system. By chance, has the ABS light turned on or brake light? This type of issue is usually related to a wheel speed sensor failing. I have even seen the lights come on due to low brake fluid, so check that as well.
If you haven't, you should really have the CAN bus scanned. CAN stands for controller area network. Basically, all the computers/modules are tied together via a few wires. By performing this type of scan, it will identify a code regardless of the module it is stored in. In this case, it could be stored in the ABS module.
Here is a video showing how it is done:
https://youtu.be/InIlnsjOVFA
That is the easiest thing to do to confirm where the problem is coming from. If you want to check each wheel speed sensor manually, here is a link that shows how that is done:
https://www.2carpros.com/articles/abs-wheel-speed-sensor-test
Let me know if you have questions. If you have the system scanned, let me know what codes are found.
Let me know what I can do to help.
Take care,
Joe
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Monday, July 12th, 2021 AT 9:54 PM