90 Suburban TH 400 Kickdown ?

[Bright Idea]

I have a 1990 V2500 Suburban with the TH 400 transmission. The kick down has stopped working. Not being familiar with the TBI setup, I am wondering where to start. I do know that there is a component internal to the transmission the has an electrical plug that is intact. There must be a switch that activates this ? Is this related to throttle linkage or from the ECM ? Thanks for your replies in advance.

 

[Vbb199]

It's a single 12v wire running to the driver side of the trans that goes to the kickdown solenoid internally, either the switch behind the gas pedal or at the tbi completes the circuit at WOT and makes it kick down. It's just like a momentary switch. You step on the gas, a constant 12v from the truck runs thru the switch and sends 12v to the solenoid

Maybe on the tbi it's off of TPS position? I know a decent bit about the tbi system, and the th400, but how they play together, I'm not sure.
I'm moreso knowledgeable on the 1/2 ton models with a 700r4 with tbi
The first line really applied to carb systems with a th400. Hopefully it Carries over.

 

[gmbellew]

I am no help either, except to point you to the GM manuals in the reference library.

 

[Bright Idea]

Thanks
Rock Auto shows a kickdown relay as well as the internal solenoid. The relay possibly gets a signal thru the ECM from the TPS ?
I will head down this rabbit trail.

 

[Vbb199]

Follow the orange wire on the trans maybe, see where it leads you