We've got a 2003 Toyota Highlander 2WD 3.0L v6, 275K miles. My Dad is the original owner. A few months ago it stopped shifting into overdrive (4th gear). Sometimes the car will shift into OD when at cruising speed but after coming to a complete stop, 4th gear is no longer available. The problem can sometimes be temporarily solved by restarting the engine. Transmission is original to car and shifts smoothly; when it won't shift into 4th, the car shifts between 1st, 2nd, and 3rd no problem.
After doing some research, we thought it was a problem with the ECM/transmission control module. We have tried remanufactured and pre-programmed ECMs with no luck. Any thoughts? Thanks!
If changing the ATF can not help, odds are that the 4th gear is going bad. Either live with it or swap it with one from a junkyard.
I once had a Blazer which was eratic shifting into overdrive and it was a defective spark plug. That affected the computer and affected the transmission shifting.
Just and idea.
