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).

[heathgu]

Yeah cougar,
thanks for the advise again. I will see what i can find. The truck has gone to my mates who is a auto sparky. See what he come up with this afternoon.

Cheers and thanks heap Heath.

[heathgu]

Hey cougar,

I have check everthing twice and i am pulling my hair out.

Could it be something like the tcm and the ecm are not from the same vehicle. Would this cause the break down in communications??

I have no more ideas.

Cheers Heath

[Cougar281]

Shouldn't, unless they changed something for the newer controllers. I had a TCM from a 2003 8100 in my truck at one time and it worked normally, except for the weird shifts. No codes, though. Did you change the VIN(s) so they all match?

E-mail me a list of the codes if you can.

[petestoy]

I have a similiar problem on a 2006 sets P0700 and U0100. reset the codes and its fine for about two weeks. Checked power and grounds at the TCM found the Transmission connector at the back of the tranny not seated it would move back and forth a little contact cleaner on all connections. The code won't clear it self from what i read so you would have to clear it manually. Mine comes on right after start. is yours similiar? Does it put tranny into limp mode?

[Cougar281]

I have a similiar problem on a 2006 sets P0700 and U0100. reset the codes and its fine for about two weeks. Checked power and grounds at the TCM found the Transmission connector at the back of the tranny not seated it would move back and forth a little contact cleaner on all connections. The code won't clear it self from what i read so you would have to clear it manually. Mine comes on right after start. is yours similiar? Does it put tranny into limp mode?

Heath's problem was a bad TCM. He also had a LOT more codes than P0700 (TCM Request MIL) and U0100 (Lost Comm With ECM/PCM A). Are those the only codes you get?

[petestoy]

That is what the dealer told me two weekes ago. the mil light came back on and its responding the same way. I ordered EFI Live on Wednesday and have not recieved it yet to verify.