Hello,
I was driving on the freeway with the transmission switch in "Sport" mode going about 60 MPH when I decided to pass the vehicle in front of me. When I pressed the accelerator down, the car made a loud bang but it did accelerate to 70 MPH. At that point the GEARBOX FAILURE warning illuminated on the dash. The car seemed to drive OK but when I slowed while leaving the freeway, it seems like it does not go into low gear; perhaps it is starting in second? I checked the OBD code and got the P1747 Pressure control solenoid A: short circuit reading. I have a diagram the shows the resistance across these solenoids to be 6-8 Ω but I have not measured them at this point though. In looking up the warning and reading various repair manuals and diagrams for the 5HP-24 transmission, it appears the solenoid is relatively easy to replace. If in fact the solenoid is shorted, is there any reason to think that replacing it would not fix the problem? Perhaps changing it and the Pressure Regulator Valve at the same time may be prudent?
The car has never had a problem shifting or made any indication that there was a problem with the transmission prior to this happening. I do have a spare transmission available if this one is actually broken but I'd prefer not to have to deal with replacing the whole unit. Any advice on the best course of action would be most appreciated! Thanks much. Dave

 

P1747 is PRESSURE REG #3.Here is some info for controls and DTCs.

 

Thanks bunch Motorcarman! Much appreciated.

 

I measured the resistance through each solenoid and pressure regulator and each one is within spec. Pressure regs readings are 6.5 to 6.8 Ω and the shift solenoids are 26.3, 26.6, and 26.7Ω. I also measured the ones on my other car and they have similar numbers. ( All of the measurements were done at the TCM connector though I'd suspect that should be an adequate point to check from.) I then swapped the transmission control module as well but it made no difference in making the car run correctly. Unless there's another great idea out there, It looks like I'll be doing that transmission swap after all. Dang!

 

When I had a fault for #1 pressure reg I did the pin check (resistance) at the TCM because you also check the harness.

I did not see a large difference between the other PR resistance measurements but the DTC for #1 PR kept 'flagging'.

I have a few faulty gearboxes so I removed the #1 PR from another gearbox and swapped it out.

Fault gone and new fluid/filter.
Car is fine for several months now.

 

Well, perhaps I'll try that first. These solenoids are essentially valves and it may be that internally the unit is stuck? I am a bit concerned about what might have happened to the transmission during the loud bang when the car shifted during acceleration. Once I pull the transmission pan down if there are no metal bits in there I may try to swap out the solenoid. Thanks much for the reply and good idea motorcarman!

 

Thank you very much Motorcarman for the advice. I replaced pressure regulator #3 yesterday and the transmission is fixed! When I stared the car, the GEARBOX FAILURE warning was gone, and after filling the transmission with fluid, it drives and shifts like normal. There we no metal splinters in the pan; just the usual microscopic bits on the magnets. Also, the fluid was surprising clean; I must have serviced that trans at some point in the past few years. Refilled with Pentosin and it seems good to go!
I have received some much appreciated advice over the years from members of this forum and this time it was especially worthwhile.



Yep, it's bad!