Forum Discussion
sjdraper
4 years agoNew Contributor
attached device may be preventing your vehicle's diagnostic test
I have been receiving from on-star "an attached device may be preventing your vehicle's diagnostic test from completing. Unplug any devices from the diagnostic port and try again later." Car w...
dbwhitsitt
3 years agoNew Contributor
Was this ever fixed? Purchased a 23 Malibu and immediately had this diag from OnStar. Dealer has tried everything and communicated with OnStar. Last resort is to replace the OnStar module but delivery for it is sometime in February. We purchased the vehicle on 12/13 and took it back on 12/16. Dealer has had it ever since.