Transmission not shifting into fourth gear?

It sounds like the revolution shaft sensor is weak, can I ask if the shift times are okay with the other gears? Also, we should run the cods to see if any are stored, here is a guide to help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

You might want to upload it and plug it in again because it might have corrosion on the connector. Here is the location. Check out the images (below). Let us know what you find.

Hi, I removed the air filter box and under I checked the connection there’s no rust. I will check the codes in two weeks when my mechanic is open. transmission is shifting second and third gear good, no problem.

Yep, lets run the codes to see if any are stored, then I would try replacing the revolution shaft sensor. Have a good weekend!

Happy new year. today I visited my Mechanic, used diagnosed tool, cannot connect to my car, checked all fuses, all okay. light is flashing when the tool is connected.

Happy new year! I would remove the electrical connector for the PCM and check for corrosion. Also, let's test the power and ground for the data connector.

Here is the video to help you:

https://www.youtube.com/watch?v=6Tlg3JmgNSQ

Here is the location of the ECM so you can check it out. Thanks for the images and video. Also, check the main system grounds at the engine, if one has broken or come loose it will cause this problem.

PCM and ECM is the same hardware?
I checked ECM Box Connection is okay, pic.1.
Checked OBD - and+ is ok, pic 2,3.
Found just 2 small ground on the left side engine.

PCM and ECM is the same hardware? Yes, if you have power and ground the scanner should communicate, did you try the scanner on another car to make sure it works?

Hello guys, after long time of the holidays of my mechanic and my holidays a got time to check my car which I am not really using because of that problem, we connected computer and it was working and showing problem of knock sensor and I believe it came one week after I was washing engine space the similar problem I got with my last car GMC envoy after washing engine space same problem to replace the knock sensors .
I don’t want to spend so much money to remove everything and replacing all the stuff there’s not just knock sensor but gaskets I have to replace, I just want to fix up that car and there is no problem with engine
My question : Can I just short cut that sensor?

Not really the computer needs the knock sensor, please start a new thread for that repair. This won't have anything to do with the transmission shifting though, has that part been fixed?