Drivesfed

08 shifting saga. Please help. 70,000 miles.

Hard shifting into 2nd and not going into 4 into at times. Replaced fluid and filter added trans tune. Worked great for 2 weeks.

Then lost 4th all together. Pulled codes po751 and 752. Using the scanner got it to shift into 4th. TCC working fine. Worked great for 10 miles after clearing codes.

Now 3rd to 4th is perfect but hard/late shift into 2nd and throws the 751 code again.

cleared codes again and same 1 to 2 hard/late.

HELP!

Oldblue

https://www.obd-codes.com/p0751

Is the fluid level full?
Any possibility of loose wires?

https://www.obd-codes.com/p0752

Seems shift solenoid is stuck off or on, it might be a burnt solenoid connector internally.

It’s possible to change the solenoids , change the TCC one also.

Drivesfed

Fluid level is full.

Oldblue

Then it could be a sticking solenoid or loose connection

donbrew

P0751 and P0752 mean, respectively, no 1st or 4th, no 2nd or 3rd.
They are both electrical in nature. Wires and connectors.

Drivesfed

Will check wiring tomorrow. Where exactly will I find the connectors?

donbrew

At the ends of wires. They all enter in one place and end at the TCM.
I guess it could be the linkage. It's kind of complicated the way they are set; If the TCM thinks it is supposed to be in a certain gear it looks for the drive ratio and throws a code if they don't match.
Hard to believe the trans is mechanically malfunctioning that way, so the suspicion goes to the sensors that tell it what gear is supposed to be in play.

Oldblue

Read this

https://www.chevyhhr.net/forums/driv...olenoid-61313/

Drivesfed

Thank you. I'd seen that post in my searches. The diagnosis in the first post is very helpful.

Oldblue

Sorry I thought I had added that link in my earlier post .