New Code on the reader !

[solidaxel]

Well I think things are happening now that there are some miles on the engine & Trans.
Po742 showed up after a long drive, 50 miles?

TCC circuit "stuck" ??

[ls1nova71]

If the torque converter is actually stuck in lock up it will want to kill the engine when coming to a stop, like not pushing in the clutch on a manual. If it doesnt, you probably have a wiring problem and the PCM is setting the code because of it.

[solidaxel]

Well it does have a surge when down shifting 3 to 2 and 2 to 1, especially when cold

[solidaxel]

Well I did check the cannon plug on the trans with a stock harness and the color code and location seems to be correct.
I guess I will have to prove it with two people and pin out the connector and the trans plug
Where else should I look for a wiring problem?
The brake light TCC plug checks out, brake on- tcc off

[BR3W CITY]

Since I love to blame tunes; if for some reason anyone played with your lockup settings, they can error out. Most of the time tuners shouldn't be touching your lockup settings unless they've had time with your setup in person (And most don't touch it at all).

[solidaxel]

Wellll as a matter of fact!

Yes we did change the lock up settings and now I find that it is "searching" at a speed that is too low, 45MPH, and I am going have him put back to where it was before the tune I think lock up was at 55 MPH

[clinebarger]

P0742...... The PCM commands TCC OFF, TCC slip RPM remains low (-20 to +20 RPM) This is not a electrical fault code.

There is no "Regulated Apply Oil" available in 1st gear...So the TCC will release upon a 2-1 downshift even if the TCC Solenoid is stuck on.

A Mechanically stuck/sticking TCC Enable Solenoid will cause this code.

The TCC Enable Solenoid is part of the internal trans wiring harness, Though you can splice in a new/good used solenoid using Red Insulated Butt Connectors to keep from pulling the 2nd Accumulator & EPC Solenoid to replace the harness.

While the Solenoid is out, Use an Awl too make sure the TCC Apply Valve is free (There is a hole in the retaining washer, Insert the Awl through the hole & stroke the Valve)

[solidaxel]

Thanks Cline
Should I replace all the solenoids and harness while we are in there?
Any tricks I should know about?

[BR3W CITY]

Cline, if thats the case, and one starts or suspects that the TCC is actually stuck on/locked, would manually putting the truck into 1 automatically unlock and act as proof-of-diagnosis?

[solidaxel]

I will do that in the A M
Then clear the code, and see if there is a difference?

[clinebarger]

Originally Posted by BR3W CITY

Cline, if thats the case, and one starts or suspects that the TCC is actually stuck on/locked, would manually putting the truck into 1 automatically unlock and act as proof-of-diagnosis?

If the TCC is mechanically stuck (Very Rare), It wouldn't matter what range the trans is in. It would be locked all the time & stall the engine etc. Which is not a symptom the OP has.

But to directly answer your question about Manual 1st Gear, I'm not 100% sure, I would have to see what the TCC PWM Solenoid duty cycle is in Manual 1st. My hydraulic diagrams indicate that regulated apply oil is present in manual 1st. But the diagrams can be wrong.....Wouldn't be the first time.

What I do know is, The TCC cannot hydraulically apply in the OD/Drive range while the unit is in 1st gear, Because I have had the TCC Enable Solenoid or the TCC Apply Valve stick & the TCC would stay locked in 2nd, 3rd, 4th gear.
Well technically, It will unlock momentarily then PWM Apply right when its suppose to. Then under Decel, It will stay locked 'til the 2-1 downshift.

Hydraulic diagrams confirm this, Or should I say my experience confirms the diagrams are correct...


I was going to post the diagrams but photobucket SUCKS, Maybe later.

[clinebarger]

Originally Posted by solidaxel

Thanks Cline
Should I replace all the solenoids and harness while we are in there?
Any tricks I should know about?

Up to you....Your other solenoids are working.

[solidaxel]

I tried it in 1sr gear and everything seemed OK
I put another 30 miles on it today and it did not throw any codes
I will get the truck back in two weeks and try the TCC apply tricks you mentioned

Thanks all for your help