Transmission Rebuild - NOW getting check engine codes

[RexSmith]

Background:

Daughter bought a used 2006 Liberty. Almost 200,000 on the ticker. A month ago - one of the clutch pack clips broke, making it require higher RPM's to get moving - especially in reverse. I changed the trans fluid/filter - (really so that I'd have an excuse to see if there were any parts/debris in the pan). Yep - chunks of the clutch pack retaining clip.

Took the Liberty to a transmission shop (national chain place here in the Dallas area) that does their own rebuilds.

Within 20-50 miles of driving after a rebuild - have been getting P0740. Always during open highway time (not in stop & go city traffic)

Have now taken it back 3 times to have it fixed... and they have replaced more parts... but so far - every time - the code keeps popping up. Doesn't seem to occur while they test drive it after performing a repair - but usually within a day of my daughter having gotten the Jeep back. (I suspect they aren't test driving for enough distance to duplicate her conditions)

First time back in, they replaced solenoid pack. Second time back in - they replaced the torque converter.... Third time back in - they replaced the valve body - and daughter got the jeep back yesterday. After about 20 miles - STILL tripping the P0740.

Monday will be the 4th time it's back to the shop. No codes were presented until AFTER the rebuild. Are there any other components in a master rebuild kit that might be the culprit? What's the monitored electrical signals that trip this code? I'm pretty proficient with car repairs - but transmissions just aren't something I've got a lot of knowledge about. Trying to understand what else could be the root cause of the check engine light...

 

[tommudd]

To determine what the actual feedback is at the TCM and if it is commanding the solenoid, you need to track the TCM using a scan tool since the TCC is only activated under specific driving conditions, thus why they are not finding it on a short test drive . To get a comfortable TCC engagement, the solenoid is controlled by the duty cycle normally.

Digital storage oscilloscopes or graphing multimeters set to the duty cycle will be needed to test if a signal is actually being sent by the TCM. The negative is probed to a good ground and the positive to the wiring harness that is plugged into the TCM. The TCM may be at fault when the cycle is intermittent or at 0 percent or 100 percent.


The most common mistakes made when diagnosing P0740 is thinking that the problem is related to driveline issues, internal transmission issues, or engine misfire issues. It’s not uncommon to assume that the torque convertor itself needs to be replaced/rebuilt, when it could just be a faulty TCC solenoid or dirty/contaminated transmission fluid. Have them check all wiring as well, could of been some pinched when removing or installing the transmission

 

[RexSmith]

Thank you. When she takes it in on Monday - we'll have their diag. guy do a LONG ride along with their computer attached to show what's going on.

To determine what the actual feedback is at the TCM and if it is commanding the solenoid, you need to track the TCM using a scan tool since the TCC is only activated under specific driving conditions, thus why they are not finding it on a short test drive . To get a comfortable TCC engagement, the solenoid is controlled by the duty cycle normally.

Digital storage oscilloscopes or graphing multimeters set to the duty cycle will be needed to test if a signal is actually being sent by the TCM. The negative is probed to a good ground and the positive to the wiring harness that is plugged into the TCM. The TCM may be at fault when the cycle is intermittent or at 0 percent or 100 percent.


The most common mistakes made when diagnosing P0740 is thinking that the problem is related to driveline issues, internal transmission issues, or engine misfire issues. It’s not uncommon to assume that the torque convertor itself needs to be replaced/rebuilt, when it could just be a faulty TCC solenoid or dirty/contaminated transmission fluid. Have them check all wiring as well, could of been some pinched when removing or installing the transmission