98 t56 ta... Issue started 1st time about 6 months ago after sitting. 1st the speedo crapped out after a hard downshift and wot. Now as soon as i let off clutch from stop I'm doing 150mhp then idle roll in 1st, needle buried. But.. the next issue is what I'm trying to see. So i have some info before taking door panels off and cutting open door jam harness.
So...
Whether driving or stopped at a light or in driveway etc... Anytime. If i hit the window switch either side up or down, the radio will cut off and windows cut out as well. Then 5-15 seconds later, everything is back to normal... All the wiring on this car is pretty much still factory. Minus the speakers in the passenger sail panel, nothing else has ever been cut off this car. o2 rear Sims added. Tuned on hptuners 10 years ago... Only thing even added to this car was the SLP line lock kit which has no issues on hidden anything or bad grounds anywhere else. I have on dozen 4th gens and six LS1 4th gens. Never have I had this issue.

Thanks in advance!

 

Check the "T" Solder in the BCM. it is probably cracked and needs to be re-soldered.

 

I appreciate that info very much. When I have moment to dig into the bcm, I will check that. Now is that for the window/radio issue or the speedo?
also, if were cracked... Issue would not be intermittent. It would be constantly.

Thanks in advance

 

This will affect radio and windows.