My 91 F 150 w/AT won't come out of overdrive automaticly. the push button over ride does work though. is it the same solenoid for both automatic function and the bypass sw? How can I trouble shoot? I am able do compensate for now by pushing the over ride manualy when needed.

 

These is no solenoid for turning on or off the overdrive. All the switch does is tell the PCM to not allow the trans to go above third gear.

Can you describe your problem in more detail? If you are at 50 MPH and floor the go pedal, does the trans shift? When you come to a stop does it downshift to first gear, or does it stay in fourth gear?

 

when cruising at about 50mph and have to lift speed drops to 45 rpm under or around 1500 truck will not rev up and accell it stays in OD or 4th gear as I slow down it will down shift eventualy into second I can't tell when. I have been hitting the OD over ride switch when needed and this drops it down into 3rd. when I checked the codes I got a 632 overdrive cancel sw not changing state E40D.

I have been having other problems that I am working on EGR is capped off waiting for me to remove a broken bolt, and had to replace air bypass valve yesterday. truck runs good when warm except for OD kickdown.

 

When you run the self test do you press the OD cancel button? If not this will set the 632 code. It's the only way to set that code.

I suspect you might have a problem with the throttle postion sensor (TPS.) That and vehicle speed are what determine what gear the trans should be in. Since you didn't say you have an upshift problem it's likely that vehicle speed is working. Does you speedometer work? It's driven off of the same sensor that drives the trans.

 

No I did not hit the switch durring the diagnostic. It shifts up just fine and the speedometer works too. Right now it is running rough when cold. I have been chasing the tuning problem a lot lately I guess its another part of that. The intake is capped at the EGR and the vaccum is plugged maybee that is affecting the tune. I have a bolt broke off I need to remove before I can replace.

 

A capped EGR certainly can affect the tune. The PCM is expecting to see EGR. I'd hold off on the tranny issue till you get that fixed.