Quote Originally Posted by DmaxMaverick View Post
P0700 is only the TCM requesting the PCM to illuminate the SES lamp, which drops the P0700 in the PCM shell DTC. It is not a error or failure, in itself. If the SES lamp is on, and you have a P0700, you need a scanner/reader capable of reading TCM data to recover the causal trouble code(s). Common "code readers" don't do this. Also, the TCM does not clear the P0700. The PCM simply expires it, if there are no further pending TCM codes, after a specific number of warming or starting cycles, depending on the code class. Transient TCM codes tend to clear themselves very quickly, and can leave behind a P0700 ghost. If possible, check the DTC's before shutting down the session it occurred. Some of them clear at the next restart if the condition is not present, and some of them do not print in history. Speed and pressure codes (slippage) remain for several warming cycles, while most solenoid timing, voltage and temperature errors may not last through 2 restarts if they don't repeat. There is also a trigger for limp mode, but I haven't figured out that one yet. I recall seeing a chart of the code classes and reactions, but can't find one now. It may have been in my Alldata account, but I haven't renewed since they priced me out of their market.
Thanks Greg. I had a local friend (and mechanics garage owner) attempt to pull the codes using his commercial Snap-On code reader. He couldn't get any detail beyond the P0700, just like my Predator reader/programmer.

Typically, the SES lamp is off for a few/several seconds after starting the engine, before it reappears. If using the Predator to reset the SES, the lamp will go out for a few/several seconds, before reappearing. I need to crawl under the truck and then wiggle the electrical connector to see if that has an effect. I do know that the SES remained off after the last full service, which I suspect may have been due more to incidental movement of the electrical connector than the service itself. The pan had been dropped during the service to R&R the internal pan filter. There was very little in the way of sludge or particles in the pan and the ATF looked pretty new.

Annotated Allison code list: https://www.thedieselpage.com/member...sondtclist.htm