GregB58

I need a bit of advice/help and you folks being some of the smartest car guys I know I thought I'd ask here. OK ... enough buttering you all up with platitudes. ;-)

My son has a 2000 Montana which threw a (I think) P0743 ODB error last evening. It said the TCC Solenoid was stuck open. They took it to a national Transmission Repair shop this morning and were told that the transmission should be replaced. I had them ask if they could just change the fluid and would that possibly help since from my online research this error may simply be dirty fluid or debris in the fluid causing the solenoid to stick. The repair guy (or more likely the sales guy) told them that changing the fluid may cause the transmission to stop completely.

Well I'm definitely not a transmission repair guru, (heck, I'm I'm not even a decent shade tree mechanic) but that doesn't sound right to me! Has anyone had this solenoid issue and if so what repair steps did you take? Any help and input would be greatly appreciated.

dmill89

By "a national Transmission Repair shop" do you mean the thieves at AAMCO or Cottman? They'll always tell you that you need a new transmission whether you really do or not. Don't let them do a fluid change either, they tend to use "universal fluid" (there is no such thing) that doesn't meet any manufacture's specs.


Have a reputable local transmission shop (not a national chain) if you have one take a look at it or a GM dealer if you have no other decent options. TCC solenoid failures are pretty common on 90s to early 00s GM transmissions, but it does not usually require a transmission replacement and should only cost a few hundred dollars to fix.


A fluid change definitely won't hurt (but just do a drain and fill, a pressurized flush, can stir "gunk" up and cause problems), but there is a good chance you will need to replace the solenoid (try to avoid driving it much at high speeds until it is fixed a torque converter not locking up will cause the transmission to run hot and could burn it up if you're not careful).

GregB58

LOL... yep it was AAMCO. We are changing the fluid and filter this weekend (not a power flush) and then see what happens. The CEL seems to be intermittent and comes and goes. If this doesn't work then I have a source for a used transmission for $200. Can't say I want to do the actual change but I can probably change the solenoids before the replacement gets put on. If I don't go the replacement route I have a couple local shops I will take it to to get a diagnosis and quote.
Thanks for the info.