I posted the question yesterday and there have been no answers so I am still looking.
The first step was that all three linear solenoids (SLS, SLU, SLT) were replaced. That did not solve the problem.
The second step was a full valve body rebuild by a professional valve body rebuild company, all of the on/off solenoids were rebuilt. The VB was then tested including testing with hot AFT and everything was passed. For warranty purposes, they also rebuilt the original linear solenoids, which are what is on the VB right now. The rebuild included all of the Sonax upgrades.
When I re-installed the valve body I replaced the two rubber seals between the VB and the main transmission housing.
On the Saab 9-5 you can remove the valve body with the transmission in the car, so nothing else on the transmission was inspected.
The transmission fluid (AFT3309) is changed regularly, I usually do it every other oil change which would be between 10 and 15K. I use only the Mobil 3309 fluid.
Car has 145K on it
Thanks, describes what is "left" in the system.
The issue is that the 03 is not worth a full transmission rebuild at this point. I love the car, but can't see sinking $3K+ into it if it's an internal transmission issue. Not only that, but finding Saab service these days is getting difficult. one of the two dealers in this area has already quit the Saab business.
Not sure what to do at this point.Do you happen to know if the Tech II has more information in it about what is happening?
The car spent some time at the Dealer this past week, they reset the TCM and updated to the latest firmware with the Tech 2. Still throws P0785 when hot.
I have done a lot of reading in the WIS about this code, the description is that when the system determines that the SLS current is out of spec it throws this code. I can't see that being an internal issue on the transmission, can you? I also saw one posting on line of someone who had this issue and had the transmission replaced and was still getting it, I don't want to have that happen to me!
My next step is to replace the wiring harness between the transmission and the TCM or replace the TCM. Where would you start first?
I have done that. The connection to the solenoid is inside the valve body and is bathed in the transmission oil. That connection was removed and re-installed when I changed the SLS and when I changed the valve body
The transmission harness then connects to the main harness with two snap locked connectors under the battery. I took both of those off and inspected/cleaned the connections and did not find anything.
The TCM is in the passenger compartment behind the glove box. I took that off the other day and there was no corrosion or moisture.
Today I drove the car till it signaled the fault (about 30 minutes) then came home and disconnected the TCM from the car and let it sit outside of the car for about 10 minutes (it is cold, probably about 50 or so) The TCM was dead cold after that.
Then I put it back in the car. The engine was still operating at temp and I'm sure that the transmission fluid didn't lose a whole lot of temp either.
In about 2 minutes, the fault came back. Makes me believe that there are no heat related issues with the TCM. Do you concur?
That leaves either the transmission or the harness between the transmission and the main wiring bundle. Unfortunately that part from Saab is NLA. I'm searching for someone who has a transmission for sale that is willing to sell the harness separately.
I'm confused as to how something in the transmission (clutch, band, etc) would present as an electrical fault? The reason I ask is that I'd hate to go to all of the trouble and expense to get the transmission replaced and then find that it didn't solve the problem.
The specifics on the P0785 described in the Saab WIS says that this is a current too high, short to B+ or short to ground on the SLS.
I did find someone who will sell me a used transmission harness, I hopefully will get that installed next week some time after it arrives.
It appears that the harness did solve the problem. I've been driving the car for three days now and have put about 100 miles (highway and local, in traffic) on it and no gearbox fault indicator or codes. I'm cautiously optimistic that this is the issue.
Wanted to let you know since this may come up again with another question.