Guys,

The coldest days this winter caused cel to come on. The transmission showed a couple of codes. "Pressure Switch C stuck open" and "Pressure to High" along with the p0700. Transmission shifts fine.
I just took it to the dealer to have it looked at. The DTC's had been reset due to changing the tune back to stock. Dealer says there's no codes ever stored in the TCM - Only codes are stored in the PCM, which are gone. Is this correct?
Thanks! -Mark
PS: He also adds that he's never seen a problem with an allison. :rolleyes:

Sticky valve in valvebody. Change your spin on, it's probably dirty from clutch material.

Guys,

Dealer says there's no codes ever stored in the TCM - Only codes are stored in the PCM, which are gone. Is this correct?


In the old days he would be right but with the Allison and the new 6-speeds they have a seperate transmission control module that is capable of storing it's own codes. So the ECM stores engine codes and the TCM store transmission codes.

Ok - But does the O5 allison tcm store codes? -Mark

The codes should be in the TCM - So the Dealer is wrong and I should take it somewhere else?

The codes should be in the TCM - So the Dealer is wrong and I should take it somewhere else?

One thing to keep in mind is that few shops get to work on the Allison and as a result they know little about them. If you can find a dealer that has some familiarity with the Allison they may be a better choice. But before I'd give up on this one I'd see if their techs know more than the guy in the front office.