Tow/Haul no worky

[GeorgiaDieselGTO]

As the title says the tow haul is not working on my Dad in Laws 09 LMM. The wires seem to be intact in the steering column, and the T/H light on the dash works fine, but its not actually working. He had it in at a dealer, and they say they cant figure it out.:hmm: Any ideas? also does anyone know what pin number those wire are in? this wiring $hit is not my strong point

 

[GeorgiaDieselGTO]

bump

 

[DAVe3283]

What, if anything, is done to the truck? Stock trans? Stock TCM tune?

The light on the dash working is very odd. If any of the TCM connectors have been disconnected, it might be worth checking that all the pins are fully seated in the connectors.

 

[GeorgiaDieselGTO]

Yes stock trans and Tcm tune. The connection to the controller had been disconected a while before it quit working. as far as i could see the pins look fine, do you know which pin number the tow haul is? I would like to check it and check the wiring from there. thanks

 

[JoshH]

The T/H switch runs through the BCM.

 

[DAVe3283]

The T/H switch runs through the BCM.

Yes, and I believe it sends a message through the data bus. I would imagine it would show a CEL if it couldn't communicate with the TCM, but it can't hurt to check the TCM connectors anyway.

I really need to update my Techline, I feel useless for anything newer than 2005

If you slap a Tech2 or FlashScan V2 on the truck, and read codes, are there any U1000 codes stored? If so, you have a data bus issue somewhere.

 

[GeorgiaDieselGTO]

Oh ok didnt know that its not throwing any codes of that nature, and everything else on the truck works fine. Think this still could be a data bus problem?

 

[DAVe3283]

Oh ok didnt know that its not throwing any codes of that nature, and everything else on the truck works fine. Think this still could be a data bus problem?

What did you check the codes with? Only things I have seen catch a U1000 code are the GM Tech2 (obviously) and the EFILive FlashScan V2. All the other scanners I have used will miss a lot of codes. I think the FlashScan even misses some modules.

If the data bus is working, then I don't know what would be wrong. Since the tow/haul light toggles, the BCM is seeing the button press. As long as it isn't borked, it would send the Tow/Haul message on the data bus. If the data bus is working, the message would get to the TCM. If the TCM is working right, it would then go into Tow/Haul. Somewhere on that chain is broken, from the BCM on. A Tech2 would catch data bus issues, ruling that out.

Maybe someone with a more up to date Techline can post the diagnostic procedures for this. I can post the procedure for a 2005, but it is probably quite different. Plus, it requires using a Tech2.

 

[GeorgiaDieselGTO]

I used a V2 for codes. and only a glow plug code there. i dont have a tech2 unfortunately and the dealer was trying to say the the DPF delete was the reason they couldnt figure it out I have switched the tranny controller out off of my 08 ( i know they are different controllers, but the same scenario with both controllers) so i guess that rules the tranny controller out.

 

[JoshH]

Are you sure it isn't working?

 

[DAVe3283]

I used a V2 for codes. and only a glow plug code there. i dont have a tech2 unfortunately and the dealer was trying to say the the DPF delete was the reason they couldnt figure it out I have switched the tranny controller out off of my 08 ( i know they are different controllers, but the same scenario with both controllers) so i guess that rules the tranny controller out.

The V2 should have seen some U1xxx codes if there was a problem. If you don't mind swapping controllers around, you might want to try swapping BCMs and see if the problem follows the BCM. Rule out one more thing, at least.

Are you sure it isn't working?

Yeah, might as well cover the basics too. What indicates it isn't working?

 

[GeorgiaDieselGTO]

Yes quite certain because it shifts exactly like regular mode in regular or tow/haul mode. We gross between 25 and thirty thousand pounds every day, and every time we start these trucks we put them in tow/haul because it really sucks to pull a load without it. I rebuilt the engine shortly before this happened, but i believe it worked after the build for a few days, but not positive. thats why i was wondering about a wire. I dont see how that would have happened, but hey anything is possible. Unless you can think of another reason why it would act like this. The converter does lock in the higher gears, so i know that the converter isnt messed up.
I have never swapped a bcm before i suppose i can just try the one off my 08, and disable security in the ECM?
Also, do you know what pin number in the TCM connector is responsible for the tow haul signal? i dont know if they use the same wire, but the tapshift does work fine.

 

[DAVe3283]

Hmm, good point about security. I think it would work if theft is disabled in the ECM. Hopefully you can find the diagrams, I can't help there.

I read through the 2005 diagnostics, but couldn't find anything useful to check that hasn't already been checked. Very strange issue.

Sent from my Galaxy Nexus using Tapatalk 2

 

[GeorgiaDieselGTO]

Well il see what I can come up with tomorrow. How come I always get the weird ones

 

[2006 LBZ]

Yes quite certain because it shifts exactly like regular mode in regular or tow/haul mode. We gross between 25 and thirty thousand pounds every day, and every time we start these trucks we put them in tow/haul because it really sucks to pull a load without it. I rebuilt the engine shortly before this happened, but i believe it worked after the build for a few days, but not positive. thats why i was wondering about a wire. I dont see how that would have happened, but hey anything is possible. Unless you can think of another reason why it would act like this. The converter does lock in the higher gears, so i know that the converter isnt messed up.
I have never swapped a bcm before i suppose i can just try the one off my 08, and disable security in the ECM?
Also, do you know what pin number in the TCM connector is responsible for the tow haul signal? i dont know if they use the same wire, but the tapshift does work fine.

Hope this helps.

 

[2006 LBZ]

Data Lines should be circuit 2500 (High) 2501 (Low)

BCM Connector X3 (light blue)

Circuit #2500 @ pin #8 and #16 (#8 TN/BK #16 TN/BK)
Circuit #2501 @ pin #9 and #17 (#9 TN #17 TN)

TCM Connector

Circuit #2500 @ pin #6 and #66 (all TN/BK)
Circuit #2501 @ pin #27 and #47 (all TN)

 

[GeorgiaDieselGTO]

Yes thats what i needed to know. Ill check those out. Thanks for all the help guys. Ill see what i can get figured out