One step forward, two steps back, help

[WRB Diesel]

Well I got the exhaust welded together and hung on Wednesday, no cat, and passed emissions yesterday with flying colors. The ’94 burb is on the road legally for the first time in 3 years. Thanks to everyone’s help, without TDP it would be a 6500 lb pile of … in my yard along with all the other dog …. However, on my way to the test I realized something’s not right in the tranny. At 65 mph I am turning 2500prm, too high correct? NO TCC lockup. What I noticed is that when I let off the pedal as the rpm’s drop I notice the TCC lock and the rpm jump down 400 rpm or so. But as soon as I touch the throttle to keep up to speed I am back at 2500 rpm. Any ideas on why the TCC is not staying locked? I have read about the brake light switch going south, could this be it? Also on my way to the test the SES light came on, not on since the test. Codes are – NO CURRENT, Historic, 78 wastegate, 84 Acc pedal position circuit fault, 99 Acc pedal position 2 (5 volt fault). Thanks for the help, one day maybe one day this will be a reliable rig….

Aryn

[DmaxMaverick]

With those codes in history, the TCC won't lock until cleared, or a specific number of start cycles have passed w/o the codes. Sounds like you disturbed a ground or connection at some point. Did you do your welding with the system on the truck? While it is rare, on-truck welding can cause issues with electrical circuits, and fry the PCM. Did you disconnect the PCM and both batteries when you welded the exhaust system? If not, it could be the cause. Otherwise, I'd suspect a poor ground somewhere, or a disturbed or forgotten connector. Wouldn't hurt to check your battery connections, too.