Ok, I live in AZ. it gets hot out here the transmission doesn't want to engage into 4th gear on the freeway nor when I have to go up hill. I had a reputable shop look at it and they couldn't reproduce the issue when test driving it before and after thier fix, nor did it fail when i drove it to them. They thought maybe it could be the temp switch inside the tranny because they couldn't find any signs of foul play inside the tranny. So, here are the issues.
Wont shift into forth when hot out or going up hill
check engine light hasnt come on
code reader say I have a bad O2 sensor
tranny shop says its not the tranny and possibly something telling it not to shift
I have had some othe electrical problems like the cruise control and A/C have kicked off and then engaged immediately during all this.
Question....what would tie all these issues together?

 

Likely a bad relay or worse, a bad ECM. Which O2 sensor is bad?

 

That I can't answer....the autozone tech told me that the reader was flagging my O2 sensor....I'm assuming the one that hooks up to the exhaust because he told they cost around $60 and that was the only one listed autozone search for my van. If there are others I am all ears. Can I get an ecm diagnosed and if so where? One more piece of information. All the wiring is stock and never hacked into after dealership battery saver mod.

 

My 2000 does something similar. It works fine around town but after about 15 minutes at highway speeds it will downshift from overdrive to drive and will not upshift back to od. After I stop and shut it of for a short time it goes back to workers fine until back on the highway...

 

Mine has done that once two weeks ago on the freeway. Tranny is running fine in overdrive and all of a sudden it down shifts and doesn't return.

 

There are usually two O2 sensors, depending on the make, year and model. Generally, there are one or perhaps two, before the exhaust enters the Catalytic Converter, and then one on the exit of the catalytic converter, which sends all this information to the ECM unit and will or should put an OBD II code out, which a scanner ought to pick up.

 

You can get O2 upstream and downstream O2 sensor for $30 dollars not $60 dollars, on many sites including Amazon. Autozone is a ripoff if they sell O2 sensors for $60 dollars. You can buy a decent scan tool for $35 to $60 dollars online. I use an Innova but its a professional scan-tool at $300 dollars. They sell cheaper versions that will work fine.

 

Oilcanhenry, you're right. Rock auto has them for about $30 after shipping. Im going to have them scan an it again today to tell me which one is bad.

 

I recently went through the valve body in my 4L60e and replaced all the solenoids and the pressure switch. The parts are easy to source and once you get the pan off they are right there.

Check out the symptoms list from the 4l60e manual.






maybe ask your shop if they checked that switch. If you trust them.

 

My tranny shop says there is nothing mechanically wrong with it after opening it.... the dealership says that the tranny is just wore out without even opening it. I would like to think that it's an electrical problem. Seeing how its intermittent. I'll check the electrical when I get it back.