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Torque Convertor not locking.....CPS relearn?

1500hdjet52

By 1500hdjet52
in Ask A GM Technician

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1500hdjet52 Enthusiast

1500hdjet52

Posted
Posted

As some of you may know I hydrolocked my engine about a month ago........separate topics.

 

I just finished up replacing the motor with a used one. All went well except the torque converter is not locking up, it worked fine before I lost the motor.

 

I'm not getting any fault codes, besides ABS light which has been on for more than a year.

 

Do I need to relearn the CPS even if I dont have any codes? Also, can I do the relearn myself or does the dealer have to do this?

 

I went back and checked all the plugs and wires on the transmission and motor.

 

Thanks,

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

From what I understand, any time the CPS is touched or disturbed in any way, a crank relearn needs to be performed.

 

Unless you have a $2k magic wand ... yep, it's off to the dealer for a good porking . Nice racket GM created there ... :nonod:

 

Can't help you with the converter. Too many damn wires on these things today - makes my head want to explode ...

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

From what I have seen, the lockup convertor requires a set list of requirements to be met before it will lockup. This is done mostly for drivability reasons. Early attempts at lockup convertors (to be specific the original lockup convertor was released by Chrysler in 77/78) would lockup based on two requirements, one being trans must be in high gear, the other was related to transmission line pressure. Was not unusual to see the dash board actually move 3 to 4 inches in total vertical travel as convertor locked up when engine was cold, and wrong spring was installed in valve body.

Reason I bring this up is due to lockup convertors now behave almost 100% in the other direction. About the only things that it does not check is line pressure and if trans is in high gear. There are many requirements to be met before it will lock up. Engine coolant temp is one of them. Make sure all the gauges are reading properely. Depending on the year, if the brake lights are on, the convertor will unlock.

 

Verify that all connectors that were used on your original engine are used on the replacement. And if there are any warning lights on, get them fixed. Crank relearn will likely need to be done, and should not cost anymore than the min labour charge at the dealer. You may be able to locate a non-dealer in your area that is able to perform a crank relearn.

1500hdjet52 Enthusiast

1500hdjet52

Posted
  • Author
Posted

From what I understand, any time the CPS is touched or disturbed in any way, a crank relearn needs to be performed.

 

Unless you have a $2k magic wand ... yep, it's off to the dealer for a good porking . Nice racket GM created there ... :nonod:

 

Can't help you with the converter. Too many damn wires on these things today - makes my head want to explode ...

 

Any PCM tuner can do this for around $50 or less. I just wanted to make sure this had to be done, and the issues I'm having are related to it.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Guess you don't live in the northeast, lol. Great deal!

1500hdjet52 Enthusiast

1500hdjet52

Posted
  • Author
Posted

Guess you don't live in the northeast, lol. Great deal!

 

Yeah, i'm in SC.

 

The Crank Relearn took care of the problem. Torque Converter locks up fine, truck starts right up and runs smoother.

 

Prices for CPS relearn in my area:

 

The Dealer wanted $100

The guy that the dealer contracts for PCM flashes and other electronic work wanted $50

The local tuner at a speed shop did it for $20

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Sometimes it is the simple things. Good that you found someone local to do it for a good price and that is fixed the issue.

 

When I got the tune done on my 2010, I did it with a spare PCM. That required a crank relearn to get the light to go off, and my local dealer did it for free, for a couple of reasons, first, I have been responsible for 25 to 30 car sales since 98 at this one dealer, and second, the tech took longer to drive to truck to his work bay than he took to do the relearn.

 

Once you find a dealer that you can work with, it is best to stick with them as much as possible. It pays off in the long run.

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