I had a suncoast III with 1058, ppe race valve and tts twin lift pumps installed a few days ago. I am running the ppe 270 tune. The truck drove fine at first, but now when you let off the throttle above 60 mph the speedo jumps around and then I get the abs light, brake light, and a dic message to service brake system. No dtc's according to the ppe. When the speedo stabilizes the lights go off and the truck acts fine until the next time I get off the accelerator. My cruise control seems to be working ok. Is my dash cluster going bad? Is my output sensor bad? Do I have some other kind of electronic gremlin?

Check your ground to the block on your passenger side from your second battery. My truck was doing the exact same thing. It was fine sometimes then all of a sudden the speedo would dance all over and abs light and some other lights would go off.

Dash cluster may be going bad. GM sent out a letter for the 2004 model year extending warranty coverage for 7 years or 70,000 miles on the instrument panel cluster. I'm waiting until my truck gets to 60,000 miles before taking it in.

I installed a new output sensor on the transfer case and it seems fine. I'm glad it was just a $30.00 part.