transmission not shifting into overdrive?

It sounds like you have a Powertrain Control Moduel (PCM) that is out because the speeds sensor is the only thing that effects that and the fact that when voltage stops it resets. I would replace it with a used one. Here is the location.

Check out the PCM diagrams (Below). They call it the ECM, Engine Control Module which is the same thing.

Please let us know what happens.

Cheers

Yep you were so right once I replaced the PCM the problem went away I got a used one for 90.00 plugged right in all good now m8. Thanks for the tip. look below

My vehicle had the 5 spd auto trans.Shifts perfectly when cold.After reaches operating temp iit loses its mind.It mimics a slipping powerglide at the first and to a lesser degree at the 2nd shift.Slow to turn into a side street and it seems to go into neutral,upon acceleration the engines revs and it doesn't engage a gear,then when does engage it may shift 2-3 times in succession.In stop and go traffic its bad.

Hi Clinton11,

Thank you for the donation.

The transmission is shifting incorrectly and it could be due to a fault with the sensors or valve body.

Did you try to retrieve for trouble codes? You can get a free scan done at Autozone to retrieve the codes.

Does the Check Engine Lamp indicates while driving?

Have you checked the transmission fluid level and condition?

Toyota 2001 Highlander 6cyl.
Transmission starts off working great. I could drive 100 highway miles with no problem. Then is I stop at a light, when I resume driving the Trans will not upshift into over-drive. If I shut the car off and restart it, the trans is back to normal. I do have a code telling me my Knock sensor is bad but I don't think that would have a conection to my Trans.
Thanks
Eggster

Knock sensor code set will put ECM in fail safe mode which will cause trans not to shift into OD.

Eggster, I am having the same exact prob with my Highlander as you were..but was told that is is very unusual for a knock sensor to go in a toyota?? they told me that that it never happens just not really heard of...very far a few I was told..so, was it ur knock sensor that caused your Highlander to not shift into OD? Can u p;ease let me know..wut u found out...Thanks

Eggster, has your issue been resolved?

I am having the same exact problem with my Highlander as described above... car drives fine until I reduce speed; then it won't go back into OD... then I shut off; restart, and I’m fine; until I reduce speed again; then I’m locked out of OD again… I was getting a knock sensor code, but was also told it is is very unusual for a knock sensor to go in a toyota... I changed mine anyway... situation improved for a while; then started again, including getting the knock sensor code again... seems impossible that the knock sensor has gone bad again... Has anyone figured out how to solve this problem? Thanks. Greasedude.

Eggster hasn't replied in almost a month, Greasedude. I would suggest having a shop perform a complete code scan, tell them both hard AND soft codes. Soft codes won't set the CEL/SES light.

I have 2002 Highlander was told ECM replaced it and still same thing no faster than 40 mph?