Just started doing this today. Im a mechanic and am STUMPED. Brake lights work so all good there. Iv taken most of the dash out doing pinpoints and have found nothing. I can use the key slot but tranny shifts crazy. It only shifts at high rpm's. Downshifts very noticeably. Now I took the trans computer out and apart and inspected it and didnt notice any burns. Nothing visible.....Plugged back up and turned key on and shiftlock works. Turn key off and then back on and shiftlock doesnt work. Leave key on, disconnect and reconnect TCU and shiftlock works. Turn key off and back on it doesnt work. What in the world?? Can anybody help??? Thanks
Bo

 

So testing when it doesn't work (pins at the interlock) vs. when it does-what is missing? Sounds like you can re-produce the issue.

 

When it does work I have ground on one side and power on the other. When it doesnt work I get power on both sides.
There is a yellow wire and a green wire. The yellow wire is a switched power source and the green wire should get a ground from the shiftlock control assy. And the shiftlock control assy gets it from the TCU via white wire with green stripe.
There is a red wire with a black stripe that goes into the TCU. When I put my test light to it and the other end of light to ground the shiftlock will work. The connector is plugged into the TCU when I do this. Im kinda wondering if its the TCU.
I can disconnect the main relay while ignition switch is turned on and shiftlock will work. I can disconnect the ECU fuse underneath the hood and reconnect it and shiftlock will work. But once I turn the ignition switch off and turn it back on then it doesnt work unless I do those things.
So frustrating!!
Gonna get back to the shop and look on alldata this morning.

 

I fixed it. It was the TPS sensor. Closed throttle was showing 2.3 volts. Supposed to be .2 volts. Replaced and shiftlock works and tranny shifts great.

 

GREAT to hear.....a good nights sleep and it came together, I guessing?