Skinny

iTrader: (11)

First off: Yank ST3500 and a tranny cooler on an otherwise stock tranny and a 3.73 gear.

Well, I've been throwing this code for a while, so I finally changed the 1-2 solenoid yesterday. Today on my way to work the code went again!! The car drives fine, all the shifts are good, but it keeps throwing this code. What else could be wrong???

A BAD T/A

There is no "1-2 shift solenoid" as such. The gear your tranny is in depends on the combination of the two.
In P, R, N & first: BOTH solenoids "A" & "B" are on.
When it's time to shift, the computer tells the "A" solenoid to shut-off, now the tranny is in 2.
Next, the computer shuts off "B" also. The tranny is in 3.
In OD, "A" is on, "B" is off.
Sounds like a bad wire/ground, something electrical.

Skinny

iTrader: (11)

Shift solenoid "A" is what I changed. The code thrown is "Shift solenoid A performance or stuck off"

There is a different code for an electrical problem, P0753.

A BAD T/A

That's true. You say "It keeps throwing this code." Did the tranny shift, etc. OK before you changed the solenoid? My point being, if it were stuck "off", you could not have 1st and 4th (OD).
Did you have the code cleared and it comes back? "Shift Solenoid A Performance or Stuck Off/ 1-2 Shift Solenoid Valve Performance."
This could also mean the "A" solenoid shift valve was stuck and you "un-stuck" it when you changed the solenoid.
Anyway, have the code cleared (not just by disconnecting the battery) and see if it comes back. If the code comes back as soon as you turn on the key, but before you start the engine, it is electrical (e.i. low voltage). That is a whole different ball game.

Skinny

iTrader: (11)

Yes, the tranny has always been fine. No weird shifts or stuck gears. Thats what I find very unusual about this. I would think that I would notice something if it were actually stuck off. I've cleared the code (with an OBD2 scanner) several times. After I changed the solenoid, I cleared it again and it came back on the next day (yesterday) I cleared it again on my way home from work last night, haven't seen it again, but I've only driven the rest of the way home since.

Skinny

iTrader: (11)

This may help, straight from my service manual:
Conditions for running the DTC:
- The gear range is D4
- The TP angle is 10-35%
- The TP angle is constant +/- 5%
- The PCM commands a 1-2, 2-3, and 3-4 shift
- The TCC is commanded ON
- The vehicle speed is greater than 5mph
- The transmission fluid temperature is 68-266*F
Conditions for setting the DTC:
- Within 2 seconds, the engine speed in 2nd gear is 80 RPM greater than the last speed in 1st gear.
- Within 2 seconds, the engine speed in 3rd gear is 50 RPM less than the last speed in 2nd gear.
- Within 2 seconds, the engine speed in 4th gear 10 RPM greater than the last speed in 3rd gear.
All of the above conditions are met and one of the following conditions occurs:
Condition 1:
- The speed ratio is 0.95 to 1.2 *
- The TCC slip speed is 200-1000 RPM for 4 seconds.
Condition 2:
- The speed ratio is 0.65-0.8
- The TCC slip speed is -20 to +40 RPM for 4 seconds.

* speed ratio is the engine speed divided by the transmission output speed

Skinny

iTrader: (11)

Still spitting that code at me... cleared it twice today...

TA/30th 1002

Skinny: based on the above responses; the PCM commands a shift electrically, within 2 secs the PCM needs to see the relevant rpm change. If not, then the code is thrown.

Do I understand things correctly? ... If so, then I have a diagnostic plan that may help pinpoint things for you. ... Let me know.

TTT for you

... Ron

Skinny

iTrader: (11)

Yes, please share your plan.

gwj

You don't by any chance have a 2001/2002 pcm, do you? Seems I remember those pcms don't like the ST3500 too much b/c the rpm change isn't quick enough - although w/3.73 gears that doesn't seem as likely to me.
FWIW, mine has thrown that code a few times only in over 40K miles of running w/that converter, and only on cooler mornings.

Skinny

iTrader: (11)

Nope... 99 PCM... Looking at the conditions for setting the DTC, it seems that the converter could easily create the correct scenerio for the code, but then I think ALOT more people would be having this problem.

FAST99Z

This is interesting, I had this code with a sy3500, stock tranny and 373 gears. I changed fluid and mine went away but now I am getting the code for transmissio component slipping

TA/30th 1002

Im thinkin the problem is either electrical or hydraulic.

If you temporarily wire in an LED at the PCM's output, and another at the trans input ....you could visually monitor the PCM's command of the shift and weather or not the voltage was getting to the trans. The LEDs should work in sync.

I have 99 Helms if you need pinouts.

... Ron

Smitty

I use a GM Tech-II for data logging so I really can't speak for the other versions out,as in EFI Live or Auto Tap.
If you can find access to a Tech-II,in transmission data there is data for the 1-2,2-3,and 3-4 shifts times read in seconds.If you were able to veiw this data it might haelp with your diagnosis.Being your car is a 99 the desired shift usually is low for these cars,less than a second.Where as 01-02 cars commonly show as alot higher,sometimes over 2 seconds.
A quality shift kit to quicken shifts may help you also.
If your pcm does not have custom programming,I would go back to the dealer and have it flashed with the latest calibrations.