4l60e throwing PO740 code HELP!!

**matt evans** · 10-26-2011, 07:36 PM

i had this trans rebuilt around 7k miles ago. We put all new suspension under the car and fired it up and the PO740 code has been giving me hell for almost 2 months now. I thought it was a shitty converter that the trans shop i had do my work but i replaced it with a yank ss3600. Now the car still has the code but for some reason it now the motor revs itself up to 1500 rpm and back to idle again and dies when you hit the brake. im lost. This has been a pain in the ass. Any help is greatly apprecitated.

**pajeff02** · 10-27-2011, 08:08 AM

Are you running a custom tune? If so, the line pressure settings may need returned to stock if you also have a modified valve body.

**Frost** · 10-27-2011, 11:55 AM

0740 means that the TCC lockup solenoid has failed open or the entire ckt (harness to and from) appears open to the PCM.

**matt evans** · 10-27-2011, 01:10 PM

the car was running fine before i did the suspension. We set it down on the ground and thats when the 0740 came up. It was doing this befor i put the yank convertor in and still doing it now. i just unhooked the the main harness to the trans and fired it up and still is doing the same thing. Im really hoping to not have to replace the trans since i just shelled out 780 for the stall.

**Frost** · 10-27-2011, 01:18 PM

It should not have anything to do with the trans... I just posted that the PCM sets that when the circuit between itself and the noid has a problem. It can be open, full time high, or full time low. That's really what causes this DTC to set.

DTC P0740 5.7 L

**matt evans** · 10-27-2011, 02:06 PM

could it be as simple as just changing out the tcc solenoid and internal wiring harness for the trans?

**smokestack** · 10-27-2011, 02:27 PM

Originally Posted by matt evans

could it be as simple as just changing out the tcc solenoid and internal wiring harness for the trans?

Yes. Went through this myself.
Frost always has the best info. Always late for me though

I have to start asking him first lol

**matt evans** · 10-27-2011, 03:46 PM

Alright ill try it and see what happens. Ether way that needs to be replaced. Ill post back on here the results as i do the work. Smokestack how lin did you fight that gremlin?

**matt evans** · 11-02-2011, 04:44 AM

Got the car fixed yesterday, turned out to be the harness in the trans. thanks for the help!! btw with the new stall and suspension its running like a raped ape!

**pajeff02** · 11-02-2011, 05:01 PM

Good to hear! How or what was the harness damage?

**matt evans** · 11-02-2011, 05:52 PM

The TCC solenoid was bad. The trans shop that i took it to first half ass wired a used solenoid in place. When i went to a Buddy of mines cousin shop he had a new harness we swapped out and it fixed it. Had to replace a 02 sensor as well but as many of us f-body owners, my friends and I have many parts under warrenty so one free sensor later im back on the road.