My TPS was going out so i replaced with a potentiometer per the sticky on this site. Seemed to work ok, then I noticed the same symptoms...randomly dropping out of overdrive. Now I can't get into overdrive at all no matter where the POT is set. My mechanic checked the throwdown cable and said it was fine. The TPS is still in place but not hooked up. Any ideas what this could be?

I've already switched the wires on the POT just in case and still no overdrive.

Thanks in advance!

 

Check the wires going to the crank shaft sensor. Had a friends truck do the same thing and the little wire holder p-clip towards the top of where the wire runs had rubbed through the wire and shorting it out. Went through 2 TPS's before we realized it was us moving the wires around that would temporarily fix it.

Aaron

 

When the OD drops out, does the voltmeter drop?

Check to see if it will start in Drive.

 

did you get a linear pot? I'm pretty sure mine is, but I can't just wind it anywhere I want. It's very sensitive and I keep it about 1/8-1/4 turn from the left. If I crank it all the way to the left it doesn't work, if I crank it all the way to the right it doesn't work.

 

I would try grounding out the o.d solinoid manually with a toggle switch. Iv'e had them go bad on me. Not very often, but it is an easy test.

 

Thanks all for the tips! I'll narrow it down and report back...

 

Just got my truck back from the transmission shop. I replaced the VSS and still no OD...I ran out of ideas after checking all of your suggestions. Luckily, the shop I took it to had a mechanic that used to own a 1st gen. What happened was when I installed the potentiometer I moved the **** around in different positions, which sent crazy reading to the computer, causing it to lock up. All that needed to be done was a computer reset. The mechanic was nice enough to place markings on my dial so I knew exactly where the upper and lower thresholds are so it doesn't happen again. Right now its shifting into overdrive at about 45 which is totally fine by me.

I suppose it is possible that the computer was locked up before hand but his explanation seemed logical enough to me...hope this info helps someone in the future.