Code 39 and Code 78

[Kick Ass Matt]

Help.
1994 Suburban, 6.5 TD w/4L80E trans

I am tripping a code 39 and 78. I looked up www.kennedydiesel.com for their DTC codes..

39 - TCC stuck "OFF"
78 - Turbo Wastegate solenoid fault

My questions is would the TCC be stuck off cause the 4L80E to NOT get into OD? I can feel 1 - 2, 2 - 3, and thats it. There is not 3 - 4 shift. At 120 KM/H my truck would be SINGING along. I don't have at tach in my truck but it doesn't feel right at all so I have to kick in my double OD (Gear Vendors) unit just to bring the RPM down.

Turbo Wastegate Solenoid. The way I understand is that the ECU sends a signal to the solenoid to open/close allowing vaccume through the solenoid itself to open up the waste gate to to build boost. I see the vaccum pump, how much vaccum is healthy at idel? 15 inches? What else does the vaccum pump drive other than the turbo wastegate solenoid, the brakes as well? Reason I am asking is I don't want to replace the solenoid and find out that my vaccum pump is bad as well. I am going in for front end work this weekend, so I'd rather fix all the problems at once rather than go dking around in circles.

Thanks
Matt

[chrisk1500]

TCC stuck off can be caused by a number of things including a bad brake switch and a bad coolant temp sensor....as well as wiring to the TCC itself...

Code 78 is usually indicative of a bad WG solenoid....but it can also be cracked vaccuum lines or a bad vac pump...

I believe you should see 25" at idle from the pump (before the solenoid) and 15" between the solenoid and the wg actuator...someone will correct me if my numbers are off by a few inches....

[Kick Ass Matt]

Well I checked the vaccum pump w/a gage, and it reads 25 inches at idle. I applied vaccum w/a hand job vaccum pump to the turbo solenoid. A slight vaccum is allowed to pass through the solenoid when its NOT energized. When I energize it with 12 V, it opens up and allows vaccum through. So I "suppose" the solenoid is still good. I also measured the resistance and it checks out to be 40 - 45 ohms. Then I scaned the truck again it was still throwing the same codes. It is also starting to puff black smoke when I boot it; like WOT (wide open throttle). But then I suppose thats normal as well for a diesel truck.

As for the TCC solenoid, thats not an animal for me to touch at all...

So I guess theres nothing more I can do now other than wait till I do my front end work this weekend and let a REAL mechanic play with it; will probably take a week or 2 to get done anyways in the mean time please keep the good comments coming in.