1994 Transport Disengaes out of OD

[mobby]

My Transport will travel oh about 4 miles on the interstate at any given speed between 60 and 75 mph fine.. But the afyer 4 to 6 miles or so the trans jump out of Overdrive and will go to 3rd gear the rpm goes up about 400 rpm. Now, if i slow down and or pull over and start back to 60 to 70 or whatever then it will do the same thing after 4 to 6 miles. Yes the CEL is on, but it says Crankshaft sensor is bad. Not sure if ts bad as i have replaced 4 times...

I was thinking mt throttle position sensor is causing this once it gets hot. But would or could it cause this .. Please help with some info..

Thanks

[maxwedge]

First get is scanned should be able to see an erratic tps, also should be scanned to confirm solenoid operation in the trans, this requires a trans capable scanner.

[fixb52s]

My 1994 3800 did the same thing. It would stay out of OD unless I turned the car off, them back on. It would go out about 4-6 miles down the higway on an extended trip. The check engine light would also come on.
I guessed the EGR valve was bad and replaced it with a cheap aftermarket one. The van seemed to run better, but the light still came on. I replaced the O2 sensor and still had the problem. I finally broke down and had it scanned (I cannot do the flash light with the 94) and it gave me an active P1406 (EGR pindle position) and stored P0740 (torque converter clutch circuit). I pulled the EGR valve out and saw it was not fully closing (cheap aftermarket). A new factory one was over $160. I ended up getting another factory unit at the junkyard for $7 and it seems fixed. No more code. I have not brought it our on a long trip yet to check the OD.

Does anyone know if the transmission is designed to come out of OD anytime there is another problem? Is this something GM built into the limp home system?

[LMP]

COdes 21 or 22..that is OBD1 for TPS high or low..prevent 4th gear(OD) and TCC(torque converter clutch) and cruise control to come ON. Now going up 400 rpm means only TCC disengages. Stepping down to 3rd gear would increase rpm a lot more.
I do not think the numerous factors described have a direct effect on this condition, but they may have an indirect effect. I would be tempted to think the TCC starts slipping wwhen transmission fluid is hot enough and then the computer disengages TCC in order not to make things worse........and I realize by reading back your post that you indeed have a code for TCC.....hence.....I think it shoud rather read "1994 Transport disengages out of TCC"....

[fixb52s]

Mine would go up a lot more more. Normally, it would be around 2300 RPM, but jumps up to around 3300. No, mine is going into 3rd. Shifting the lever from D to 3 had no effect. The cruise control still would work fine.

I took it on a 50 mile trip today with no repeat. The CEL stays off, and the van is purring like a kitten.

I read the post about how the TCC would disengage with the heat up. I would also think that in this case, the cruise would also quit, right? Besides, when it would go out of OD, the CEL would always be on.

That is why I asked if the EGR would "trip" the no OD function.

I don't know where you got that code 21 or 22. I cannot get the OBD1 codes using the lights because I have an odd one that requires a scanner.

[LMP]

My reply was adressing "mobby",s case, specially about the 400 rpm.
code 21 and 22 are from '93; I think first'94 series could still use the AB jumper to read codes, after that connector B has disappeared and yes the scanner is needed. FOr those confortable with an electronic hobby, the interrface that links to your laptop computer is available here:
http://www.pontiac-interface.de/index.php It works with pre-93 as well as '94 and '95 until OBD2 arrives.

[mobby]

The other issue was the Computer was BAD it kept giving out wrong codes and wrong diagnostics...I replaced the computer and all is fine. It will go for long time then the check engine light will come on. When i stop at the store or something and turn off engine then and then i restart it the light does not come back on till I drive for and other 30 min or so.. And yes the Transport still drops out of OD after 4 to 6 miles or so and RPM goes up about 400 rpm or so when it drops out like that.

Oh and by the way.. when it jumps out like that the cruise still worked this time.. Times before it hasnt..



I havent taken it to shop to get codes read cause Im poor right now after spending all kinda money on this thing. I replaced the TPS, crankshaft sensor, camshaft sensor, fuel pump relay, fuel pump and strainer, plugs and plug wires.
Van runs great, buth has that issue with CEL periodically and of course the OD. Should I replace the EGR you think?


Thanks
Mobby

[maxwedge]

This should be scanned on a trans capable scanner to confirm o/d operation and solenoid function, if the solenoid disengages during the scan the tps can be observed and/or related codes. A freeze frame of the code can be used to see the conditions the code set at.

[fixb52s]

I would get a good scan prior to replacing anything else. There is something there if your CEL comes on. I ran my van for almost a year with the stupid light coming on and finally decided to quit guessing.
My big concern is aftermarket parts. The EGR valve I bought was brand new, but was not an AC/Delco, it was Wells. I heard others say the quality of aftermarket emmissions parts is crap, and now I see why.

[mobby]

Took it to tranny shop they said it has code 740 Torque converter clutch (TCC) Failure.

Is this bad can i replace easily or do i need to get other tranny?

[mobby]

Took it to tranny shop they said it has code 740 Torque converter clutch (TCC) Failure.

Is this bad can i replace easily or do i need to get other tranny?

mobby

[LMP]

P0740 - TCC Enable Solenoid Circuit Electrical
SO...as I read that, this is on the control side. In this case, repair could be made from the outside.

[mobby]

Hmnnn, OK... Tell me what ya think I should do...

I drove today for 29 miles with no OD RPM's at 3k or 3.5 k all the way made my engine very hot and killed my gas milage....



:P

Mobby

[LMP]

Just do a search with google for P0740.....remember this code if for TCC, not 4th gear....you will see there are a lot of references to this problem, for several brands of cars, most not very encouraging, several with a complete transmission rebuilt and..the code P0740 still coming after thousands of $....!!! ..implying the problem can come from outside of the transmission..like bad connector.
Personnally, I'd try to see if I have electrical continuity for the two TCC solenoid coils on the transmission side of the plug... B to E, and A to D: on this one, correct polarity of the tester wires are important because of the diode: normally apply red lead to A and black to D...(however some testers are inverse polarity on the resistance range,but at this low resistance value, it might also make no difference).
ANd then E to F is for SOlenoid A, and E to J is for solenoid B. SOlenoid A is required for 4th gear.
Each should read around 10 ohms
www.avigex.ca/xport/transaxle.jpg
www.avigex.ca/xport/transaxleconnector.jpg
www.avigex.ca/xport/transmission ranges.jpg

[mobby]

The garage also said i had 3 other codes but they werent active..
341, 321 and 361. he said they were stored inactive codes.

But my CEL will come on sometimes then after i turn engine off the light wont come back on for a long time..

wierd huh

thanks

mobby