P0740 code

[mglsite1]

I got a P0740 code the other day on my van. Checked the wiring and plug and it looked good. Van drives and shifts good. Ordered a 'New' Genuine GM TCC solenoid from Amazon. Drained fluid and removed pan while waiting for my part to arrive. Part arrived but smelled like trans fluid already, so much for Amazon's truthfulness. Checked ohms and original seems to be OK so I reinstalled it and will be sending my 'New' part back.
Cleared code but it came right back without even driving van. Could it be an ECM or TCM problem?

I can clear the code but it comes back as soon as I turn the key on even without starting it

I can make it work with my bidirectional code reader and it seems to work fine but ECM doesn't seem to command it to lock up.

Any help would be appreciated

 

[mrrsm]

Welcome to GMT Nation...

You refer to a Van...but your Profile lists a 2000 Chevrolet S-10 Truck. Please elucidate...

These ATSG attached PDFs are "The GM Transmission Repair and Trouble Code Bibles" that will provide additional Diagnostic Procedures that will help in running this issue down:

 

[mglsite1]

Welcome to GMT Nation...

You refer to a Van...but your Profile lists a 2000 Chevrolet S-10 Truck. Please elucidate...

These ATSG attached PDFs are "The GM Transmission Repair and Trouble Code Bibles" that will provide additional Diagnostic Procedures that will help in running this issue down:

Thanks, it is an Astro Van but I didn't see it listed when I was signing up.
Thanks for the info, looks like I have some reading to do

 

[Mooseman]

You should check continuity from the transmission connector to the other end (PCM and 12v+). Go to this website and get the schematics.

Automatic Transmission Control Schematics — 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W Service Manual | Operation CHARM

Detailed repair manual for the 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W.

charm.li

If continuity is good from the PCM to the tranny connector and 12v+ is also getting there, there might be a problem with the wiring inside the pan to the TCC solenoid itself. There is also a TCC PWM solenoid which may also be at fault so check it out. Check in the manual what the resistances are supposed to be for those solenoids and check them out.

 

[mglsite1]

You should check continuity from the transmission connector to the other end (PCM and 12v+). Go to this website and get the schematics.

Automatic Transmission Control Schematics — 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W Service Manual | Operation CHARM

Detailed repair manual for the 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W.

charm.li

If continuity is good from the PCM to the tranny connector and 12v+ is also getting there, there might be a problem with the wiring inside the pan to the TCC solenoid itself. There is also a TCC PWM solenoid which may also be at fault so check it out. Check in the manual what the resistances are supposed to be for those solenoids and check them out.

I checked the ohms on the old TCC solenoid and it showed like 2.3 so I swapped it out for one I got off of Amazon and an internal wiring harness I bought. When I checked it, it showed a good 24.3 ohms. I just installed the solenoid instead of the whole harness because I thought that I had it and I didn't want to go through all the work of swapping it out. But no, the code came back.

I can still lock up the TC with my scan tool though. Being retired, I was enjoying the hunt but I might be beating me. It may be time to take it to a professional

 

[mrrsm]

I've been Thinking about your comment...

..."looks like I have some reading to do"...

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[mglsite1]

I checked the ohms on the old TCC solenoid and it showed like 2.3 so I swapped it out for one I got off of Amazon and an internal wiring harness I bought. When I checked it, it showed a good 24.3 ohms. I just installed the solenoid instead of the whole harness because I thought that I had it and I didn't want to go through all the work of swapping it out. But no, the code came back.

I can still lock up the TC with my scan tool though. Being retired, I was enjoying the hunt but I might be beating me. It may be time to take it to a professional

When it stops raining and dries up I guess I will drop the pan again and change the internal wiring harness out and if that doesn't fix it it's off to the shop with it. After all it does have 230k on it so I can't really complain.
What do ya'll thing about something like an Auto Zone rebuilt vs a local shop rebuild?

 

[mrrsm]

Depends upon the Warranty Offers.... Start searching based strictly upon who carries the BEST Warranty and you might be surprised by what you find local to you.

 

[Mooseman]

Local shops tend to be better built as word of mouth can get around real fast if they are failure prone. Warranty or not, you still have to either pay for the labour or do it yourself. The local shop, if they also do the install, would not want a comeback and have to eat the R&R labour on top of another rebuild. They usually upgrade and replace everything to higher specs whereas parts store brand rebuilds, done by ???, they would just rebuild it to stock and reuse parts as much as possible.

 

[mglsite1]

Local shops tend to be better built as word of mouth can get around real fast if they are failure prone. Warranty or not, you still have to either pay for the labour or do it yourself. The local shop, if they also do the install, would not want a comeback and have to eat the R&R labour on top of another rebuild. They usually upgrade and replace everything to higher specs whereas parts store brand rebuilds, done by ???, they would just rebuild it to stock and reuse parts as much as possible.

Depends upon the Warranty Offers.... Start searching based strictly upon who carries the BEST Warranty and you might be surprised by what you find local to you.

Local shops tend to be better built as word of mouth can get around real fast if they are failure prone. Warranty or not, you still have to either pay for the labour or do it yourself. The local shop, if they also do the install, would not want a comeback and have to eat the R&R labour on top of another rebuild. They usually upgrade and replace everything to higher specs whereas parts store brand rebuilds, done by ???, they would just rebuild it to stock and reuse parts as much as possible.

Thanks for the info
I may just run it like this for a while if I can't get it figured out, it shifts good, the TC just won't lock up. The only problem is my MPG went from 14 to 12.
Got to love those 4.3's, all the power of a 4 cylinder with the MPG of a big block V8

 

[mglsite1]

You should check continuity from the transmission connector to the other end (PCM and 12v+). Go to this website and get the schematics.

Automatic Transmission Control Schematics — 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W Service Manual | Operation CHARM

Detailed repair manual for the 2000 Chevrolet Astro Van L AWD V6-4.3L VIN W.

charm.li

If continuity is good from the PCM to the tranny connector and 12v+ is also getting there, there might be a problem with the wiring inside the pan to the TCC solenoid itself. There is also a TCC PWM solenoid which may also be at fault so check it out. Check in the manual what the resistances are supposed to be for those solenoids and check them out.

WOW.. Thanks for the link, I will defiantly save it