P0740 fault code, 2000 Sonoma

[Jet Mech]

I have 2000 Sonoma SLS Extended Cab, automatic transmission with 4.3 engine.
Here's the issue. The Service Engine Soon light illuminated so I scanned for codes. The only code that came up was P0740 "Torque Converter Clutch Solenoid Circuit Open". Removed and replaced the solenoids and reset the the code but the SES light comes back on almost immediately, with the same code P0740. I checked for power to the solenoid and it checks good. The vehicle drives and shifts normally.
Is something else I need to look at and will I create any damage if I continue to drive it as is.
By the way, there is 146,000 miles on this vehicle. I bought this truck brand new and so far this the the only issue Ive had.
Any help would be appreciated.

 

[Molson02536]

I have 2000 Sonoma SLS Extended Cab, automatic transmission with 4.3 engine.
Here's the issue. The Service Engine Soon light illuminated so I scanned for codes. The only code that came up was P0740 "Torque Converter Clutch Solenoid Circuit Open". Removed and replaced the solenoids and reset the the code but the SES light comes back on almost immediately, with the same code P0740. I checked for power to the solenoid and it checks good. The vehicle drives and shifts normally.
Is something else I need to look at and will I create any damage if I continue to drive it as is.
By the way, there is 146,000 miles on this vehicle. I bought this truck brand new and so far this the the only issue Ive had.
Any help would be appreciated.

Check the ground wire, The TCC (torque converter clutch )circuit open code throw above 50mph when the TCC doesnt engage. This is not a big deal but will cause gas milage drop cause the TCC it designed to 'lock' the motors input directly to the trans to not allow the normal slippage that the torque converter posesses naturally. RPMs lower when its engaged and it saves gas milage. Could be the wiring is loose or a bad TCC solenoid but you replaced that as you mentioned.

Re-check the wire harness on the transmission to ensure there is no corrosion damage or a broken wire.

Good luck and keep us posted.

Molson02536

 

[Jet Mech]

Update: Since my original post I have replaced all the solenoid valves "AGAIN" as well as the wire harness inside the transmission. I also replaced the ignition harness under advise from another forum. I have checked and rechecked the wire harness from the transmission to the ECU and there are no defects. If anyone has any ideas i'm listening.

 

[Jet Mech]

Final update: After months of trouble shooting I finally broke down and replaced the ECM. I had to take the truck to a qualified garage so the ECM could be reprogramed but I'm happy to say that the "Service Engine Soon" light is finally extinguished. Apparently when ever the torque converter clutch solenoid shorted out it took the ECM out also. My Sonoma now has 147,500 miles on it and is once again 100%. Thanks to all who helped and I hope this is helpful for anyone that is experiencing the same problem.

 

[peggyannmitchell]

Final update: After months of trouble shooting I finally broke down and replaced the ECM. I had to take the truck to a qualified garage so the ECM could be reprogramed but I'm happy to say that the "Service Engine Soon" light is finally extinguished. Apparently when ever the torque converter clutch solenoid shorted out it took the ECM out also. My Sonoma now has 147,500 miles on it and is once again 100%. Thanks to all who helped and I hope this is helpful for anyone that is experiencing the same problem.

 

[peggyannmitchell]

Final update: After months of trouble shooting I finally broke down and replaced the ECM. I had to take the truck to a qualified garage so the ECM could be reprogramed but I'm happy to say that the "Service Engine Soon" light is finally extinguished. Apparently when ever the torque converter clutch solenoid shorted out it took the ECM out also. My Sonoma now has 147,500 miles on it and is once again 100%. Thanks to all who helped and I hope this is helpful for anyone that is experiencing the same problem.

Hi Jet Mech, I have been through the same code P0740 you went through. So I am looking at your ECM answer. I did not replace my clutch solenoid, or my torque converter clutch solenoid, because there is no noticeable problem with the gear shifting. (I did replace my ignition switch as advised by someone else.)
I wondered about the reprogramming done on your ECM- What type of place did you go to have it done? And what was the cost. I am looking on eBay to buy one, I can either get it pre-programmed to my vin or take it somewhere as you did. Thanks