Hello folks. I wanted to know has anyone ever experience DTC P0700 (Transmission Control System) on their H2 Hummer? If so, what did you do to remedy the situation, and how much did it cost you?

 

what year is your H2?

 

2009. Sometimes the check engine light goes out, but when it comes on, the tranny will slip out of 3rd gear into 2nd, and will stay in 2nd gear. A friend of mine took his scan tool, clear the code, and the Hummer ran perfectly fine again. As soon as the check engine light comes bad on, the same cycle happens again.

 

Bulletin No.: 08-07-30-021H

 

Thanks, for sending this Service Bulletin documentation to me. I just got off of the phone with a transmission specialist. The technician told me that the tranny is fine, but the issue lies within the electrical system itself. The tranny tech, did tell me in order to pinpoint where the issue is at the process could hours if not, days to find the actual fault in the electrical system. If anybody has any ideas on what I should do next besides get rid of this Hummer, let me know.

 

roll up your sleeves and get to work on the service bullitin? it does have pretty pictures.

 

Have a 2006 & mine was in the harness leading from the transmission up to module in engine bay area. Just a very slight occasional grounding of one wire was all it took.... once wire was located & re-insulated problem was solved. Plastic spiral Wiring loom had deteriorated on mine allowing a wire to intermittently kiss the frame to ground.

 

I appreciate the feedback everyone. Troubleshoot is what I will do.

 

GL & Update!

 

P0700 is a tcm code telling the dash to illuminate the mil. If the tcm couldn’t communicate with the rest of the network like the bulletin suggests, it would not be able to throw a p0700 and throw a u-code like what’s in the bulletin.

You need an advanced scan tool like a tech 2 to read transmission codes and actually get a direction on where to start. If p0700 is the only code you’re getting with a generic scanner, I’d be willing to bet your issue is with the tehcm inside the trans or a mechanical failure. 08-09 trucks are pretty good at both of those things. Ask me how I know.

First thing I would do is check the fluid by dropping the pan. If it’s full of metal and clutch material, you need a rebuild, if not you might get away with just replacing the tehcm.

definitely keep us posted.