Hi, I have a 99 Blazer that is showing code P0753 which is the 1 2 shift solenoid. I have changed both of the solenoids TWICE and also the ignition harness (heard that could be related) the code still comes up. The transmission still seams to be going through all the gears the only issue i have experienced is sometimes going up a hill it will not downshift. Anyone have any experience with diagnosing this? don't want to throw any more parts at it if i don't have to. I have heard the engine computer can also be related.... Any way to test that?? Thanks in advance!!!

Also sometimes when i start the vehicle the check engine light is off but as soon as i start moving within 5 seconds it will come back on.

 

P0753 - Shift Solenoid A Electrical

Have you tried testing the wiring to/from the solenoid?

 

not yet. I will. that link will give me a few things to check tomorrow. I'll repost when i find something out. Thanks.

 

ok worked on it all day... figured out its probably going to be the internal wiring harness. Went to the dealer and they wanted $250. Auto part stores couldnt get it. Found it on ebay for $50 shipped. As soon as it comes in i'll change it and update the status. Thanks!

 

ok the harness came in and i took everything apart except i cannot get the main part of the harness out. Is there any trick to unplugging the internal wiring harness on the 4l60e????

 

Update: Problem is fixed. Turned out it was the VCM, bought a reman one from advance and had it flashed at the dealer. No more light!