My 08 hhr was malfunctioning due to its tcm. At running temp speedo would drop off at 20 when slowing down. Would have to get rpm tp 3 or 4 grand before it would shift. Gas gauge and rpm would sway n flicker also .Powersteering and service traction messages would appearas well .During the replacement i accidentally touched the tcm to the positive post on the fuse box so i disconnected the battery before installation of the new one . Buttoned everything up but still have the messages and now it would read the speedo, outside temp or gasmilage. Advanced code reader said lost communication with tcm/ecm and i don't know what else to do .Anyone able to help me outout ?

 

Lost communication usually means a wire or a connector pin. Sounds like you may have blown a fuse (#43 under hood).

 

i checked all fuses and relays in the fuse box and the bcm inside but what would i look for when checking the connecters .

 

Look for pins bent/damaged pushed out the back etc.

How did you check fuse #43 under hood?

 

I have a multimeter ,thats how i checked them cause by visual inspection all seemed to be in tact the big block lookin ones obviously cant be done inthat fashion.

 

Have the recalls been done? Check fuse #29 under hood, for the OBD2 port power. Were there any codes before (like the vehicle speed sensor)?

You might take the fuse box apart and check the connectors on the bottom, add dielectric grease. At least push all of the fuses and relays down and tighten the bolts, they are usually loose from the factory.

I am guessing this is a typo? "now it would read the speedo, outside temp or gasmilage"

 

No i haven't done the recall n yes thats was a typo with the old one it would read those things but the new one wont n ill try taking apart the fuse box i thought about it thinking that total disconnection n reassemble would help.

 

The new TCM needs programming. I think they come blank, so you need firmware from GM.

The power steering might be covered by the special warranty. The ignition recall might have something to do with it.

 

I got the tcm off ebay n it came off another with only 50k miles would it need to b programmed to my car, i guess thats why ppl say never put off getting recalls done lol.

 

I am not sure about programming, all the book say is do it.

Did your reader just say that it lost communication, or code u2106/u2105.

That and joining the other 25 dead folks.