2000 P0742 OBDII code Toque Converter Clutch

This post is a continuation of my original post. http://www.automotiveforums.com/vbulletin/showthread.php?t=1016652
I reposted it with a more descriptive title:


Updated info:

130k miles.

I am truly hoping that you wizards out there will tell me there is still more that I can try and that I don't need a new tranny. But I am not holding out much hope based on other threads I have read. I just spent about $1500 in parts and dozens of hours of my own labor this spring to get this car to a point where it was running perfectly, needed nothing and would last me at least another 2-3 years. Now I get THIS thrown at me !!!!!!!!!

Vehicle is back home. I had it scanned, confirmed the previous diagnosis: P0742 TCC / brake switch stays high.
Here are some more symptoms / observations / tests I have done since I am home now.

1. SES light is out (it was reset /cleared yesterday after the scan. The P0742 was the ONLY code set.

2. The transmission shifts beautifully through all gears, all of the time. The trans fluid is reasonably fresh, is bright red, and has no odor of burning whatsoever.

3. Driving it to work today, when TCC locks up (I presume a few seconds after getting into 4th, and not under much load) there is a noticeable "lurch / stiff shift" when it locks up. Not smooth the way it used to be. This only happens during lockup. The rest of the shifting is very smooth.

4. When the trans was functioning normally I used to be able to purposefully get the TCC to unlock by accelerating slightly and stepping on the brake to activate the switch. You would be able to hear the engine rev slightly higher when you stepped on the brake to "unlock" it. It does not do this now. There is NO CHANGE in the engine speed when I do this.

5. That said, if I drop the shift lever out of drive and into "3", (I realize that the TCC won't lock up in "3"), and then do the same test as in #4 above, I DO hear the engine rev (I presume from a slight downshift) when I step on the brake. Thus, I believe this proves the brake switch is good. Doesn't this also tell me that the TCC and solenoid are working ok as I can "manually" get it to disengage by shifting to "3" ?

What else can I do to further isolate this issue?

I found this on the internet: http://autorepair.about.com/cs/troubleshooting/a/aa061701a.htm

It appears to be a good troubleshooting aid, but I can't tell if it actually applies to the Venture Transmission. It only says "GM". Any thoughts?

Does my issue sound like it is (for certain) the TCC solenoid? Or could it be external? I hate the thought of a new transmission. This one works great except for this new issue. I have always maintained the vehicle very well and never abused it. I have had it since new.

I saw where one person tried some Seafoam for a hundred miles or so, and then had a full trans flush and said he had good success? Is this worth a try ? Or am I just going to add on another $100 cost for what is inevitably going to be a "new transmission"?.

Thanks for all your help.

Acording to the diagnostic chart this is most likely caused by a short in the wiring to the Transmission Fluid Pressure manual valve position switch. "The TCC release switch is a normally-closed switch. When the TCC is released, TCC release fluid pressure opens the TCC release switch which opens the TCC release pressure circuit. When the voltage on the circuit is high (switch open), the PCM recognizes the the TCC is no longer engaged. If the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets." A subscription to Alldata online for this vehicle might be a big help on this one. I think it is under $30 for a one year subscription. You may need the wiring diagrams and pin-outs to properly diagnose where the problem is. The code doesn't have anything to do with the brake switch on the brake pedal, it has to do with the TCC brake switch that tells the PCM when the TCC is disengaged. When you did all of your other work, is it possible a wire got pinched or possibly burnt, etc...?

DewayneP,

Tnx for the reply. I actually have the manual that details the wiring and the logic (I don't have a scanner, but was thinking about purchasing some laptop software that would do this for me. I want to get a package that will work with most if not all of my vehicles.). Any suggestions?

I drove the van yesterday for about 100 miles of various road conditions. around town, highway, etc. The symptoms keep changing. it's tough to duplicate anything with any degree of consistency.

I tried to duplicate the SES light coming on, but can't. The only thing I noticed in the performance of the car over the hundred miles is that either when it shifts to 4th, or TC lockup, it is a "stiffer" shift than usual. Not a clunk, or sharp bump, but a stiffer shift. Almost like it had a shift kit in it for this one shift point. But I really can't tell if it's 4th or TC lockuo.

I was reading the manual and I found that there a bunch of conditions that have to be met in order to get TC lockup. I am stil lunsure as to exactly how to duplicate the issue, and test for lock/unlock by stepping on the brake as in my first post.

One other thing happened yesterday, and it happened only once. I was stopped at a stop light (in "D") and when I gave it some gas, it "clunked" sharply into engaging first. Shifted fine from then on.

I don't know if there is a code set or not, but I have no SES light. I am going to drive it more and see if I can get more symptoms before I take any action.

If I decide to have the van fixed, what is the best route to go. I am not up for tackling this job myself. I have a reputable mechanic that I use (when I don't do the work), but I don't think he does transmissions.

Is it best to just replace the bad parts and the usual seals etc, or is it advised to do a full rebuild? What does a full rebuild entail? I am hesitant to give the transmission up as I have had it since it was "born". I know all the ins and outs of it. It has good "bones"...

Thanks....

How about the PCS? Maybe a bad valvebody?

Lesterl,

I am considering your valve/valve body theory.

About 2 months ago, one of the front ATF lines that go to the radiator developed a pin hole and leaked some fluid out. Especially under load. It was a Saturday and I couldn't get the correct hoses from the dealer. I simply cut out the 3" piece of steel (rusted/rotted) line, and added a 5 inch piece of rubber transmission line. I flared both steel ends, and I used two hose clamps on each side. I added 2 qts synthetic ATF Dexron VI. All has been well until this weekend.

How small are the passages in the valve body? The manual makes them look pretty large. The reason I ask, is that if by chance a small speck of rust came off the outside of one of the lines I repaired, could it be enough to contaminate the valves/valve body.

If so, perhaps a good flush might solve this issue?

Can I get to the valve body easily (or is it a pull-the-transmission type of job)?

Thanks

........

The Valvebody passages are decent enough in size, the solenoids could be contaminated with a speck of dirt/ rust tho.

The Valvebody sits on the drivers SIDE of the transmission, you have to pull the drivers side axle and have the pan come off the side (trans out of car/or dropped low enough to do so.)

The valvebody is made of aluminum and some (I know the RWD ones wear the sleeves where the valves ride and they bypass fluid pressure causing issues.)

Have you tried any TransMedic/TransX or some transfix in a can stuff? It has helped prolong intervals on mine.