02 zr2 shifting issue
 

Alright gents I have a 02 zr2 and having some shifting issues. When I first start it up and put it in D it will take off in first but jump to OD them back to 1st then 2nd then OD and back and so on u till it hits OD . Then after that it shifts fine, can stop and start all day long and won't skip a beat. Then I shut it off and turn it back on it does it again then is fine. If I let it idle some it will shift fine without going thru the first issue. Is it the PCM erasing the fault when I shut it off then has to relearn it every time? Has any has this issue before? I don't think it's the trans bc it do it all the time. Thanks.

I would like to help but I’m not understanding your problem correctly. Sorry I’m old. Lol!

No problem buddy,
When I first start up the blazer, put it in drive and take off it will take off in 1st gear. But it would jump to overdrive then back to 1st gear, then shift up to 2nd then overdrive then back to 2nd. It will do this all the way up overdrive and drive fine. After it does this. I can stop and start all day without it jumping to overdrive when it shouldn't. But if I shut the blazer off and park it park. I can start it right back up and it will do the same thing, so I know it's not the trans not being hot and causing the issue. It has to be electrical or what tells the trans to shift.

Thanks, man that is a good one. Do you have a check engine light on? How are you determining it’s going to OD when it is acting up? Sorry for asking so many questions but this is not something I have dealt with that I can remember. Thanks

There is a check engine light on but it's for a O2 sensor. At first I thought the engine cutting out because it would surge. If I manually put it in 1st it will take off fine, I can only think it skips up to OD or a higher gear then back down to the correct. But it's funny bc it goes away and does fine after it does it once. Like the computer learns the fault, corrects and does fine. Then I shut it off and it clears the fault and has to relearn it. I know I'm at a loss too.

I have no answers for you. Sorry,something I’ve never dealt with. May want to find shop that can monitor the data stream to see what is being commanded at the time this is happening. Do you have to pull it in manual low every time to start out?