Quote Originally Posted by DmaxMaverick View Post
That is curious. If I'm understanding, you are clearing DTC's while running(?) and it reappears in the same session before changing any conditions (such as driving, changing gear selection, restarting)? That is not a transient fault, and it should be, at least, leaving a trail of codes in history. If you aren't seeing limp mode, the P0700 is a soft code, and shouldn't be persistent as it is. Any code that repeats after clearing, in the same session, or a specific number of successive sessions, will print in history. A Snap-On code reader, if that's all it is, shouldn't be able to read TCM codes. They're intended for general ECM DTC's and emissions inspection readiness. I use a Zurich ZR15S, which is a full function bidirectional scanner. It easily reads TCM data and DTC's, as well as historic codes, pending codes (incomplete tests), and all the real time data any of the control modules are capable of showing. A bidirectional scanner may be required to command the TCM to dump it's codes and data, which is true for most other control modules (BCM, ABS, SRS, etc.). I got the scanner primarily to access EV functions and data. GM EV's have a few more control modules that most code readers and many scanners don't know about.
I don't think the code clearing was done while the engine was running. But, the P0700 (and SES lamp) does return a few seconds after clearing and then re-starting. Of course, the code is read after shutting off the engine. I know I tested the "check/reset" with the engine running a while back, but I don't remember the details, as to whether I could clear it or not with the engine running.