Truck wont shift and getting a U0100

[heathgu]

Hey guys,

I am getting a U0100 tcm lost communication with ecm/pcm. Also the speedo is dead and the truck will not shift out of 1st gear i assume.

Any ideas or some one to speak with would be appreciated.

Cheers Heath

Or is there something i can do in efilive to help get a better picture of whats happening???

[Cougar281]

IIRC, U0100 is a CAN2/GMLAN code. Check your GMLAN wires, make sure they're properly seated and such. You have a second TCM to try?

[heathgu]

Thanks cougar,

I will have a look at the wiring and see what i can find.

No i dont have a spare tcm module that i could try.

Cheers Heath

[Cougar281]

Any chance a pin got bent? Just FYI, the GMLAN pins on the ECM are C2-44 & C2-57, TCM is 6 & 27 (also 47 & 66 go to the GPCM).

[heathgu]

Will check it out right now.

Cheers Heath

[Cougar281]

Would you happen to have a "dead" accelerator pedal too?

[heathgu]

I did have a dead accelerator pedal when i first got it going but that was from simply not being plugged in.

I will see what other codes are coming up also and let you know.

Cheers Heath

[Cougar281]

Another thing, check the termination. With everything plugged in, you should have 60 Ohms across the GMLAN High and GMLAN Low.

[heathgu]

Hey cougar,

Yep i check that and guess what it was spot on 60 ohms.

Also i had it on a tech 2 yesterday and it had every transmission code just about is this to do with the communication break down or something in the trans.

Cheers Heath

[Cougar281]

If you cleared the codes, do they come back? Also, stupid question; Is it possible the main plug by the transmission is disconnected or not seated right? This sounds almost like the transmission isn't connected to the TCM. If you remove the TCM from an Allison transmision and put it in gear, you'll get forward (One gear; 3rd IIRC) and reverse. That's it. The only time I've personally seen tons of transmission codes is when stuff wans't connected (In my tinkering, I've connected a TCM to the truck with ONLY power, gound, ign and the data busses and it threw a laundry list of codes).