Cadillac Repair: 1991 Cadi Eldorado 4.9 overdrive, work question, auto button

Question
My Transmission will not shift into overdrive all the other gears work fine..Gears 1,2,3 No Overdrive. I replaced the modulator for 22 bucks and it's still the same. Now what do I do? Any help you can provide will be greatly appreciated. Thank you. Ralph.

Answer
the most over looked item is the correct air pressure in your tires. Don't laugh, I have seen it many times.

question: does the cruise control work ?

question: is or has the check engine light ever illuminated on the dash ?

Question: do your brake lights work ?. Don't say YES, GO and LOOK.

Also perform this test:

with the engine running, On your climate control panel you will see an OFF and WARMER (high fan ^ button. Simultaneously push and hold these 2 buttons inward for 3 seconds and then release the buttons.

Now, Drive the car and get up to 55 to 60 miles per hour and see if the HI letters illuminate and let me know.

Now, Push the AUTO button and your done.


Let me know your results.