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post #1 of 17 (permalink) Unread 09-03-2019, 05:54 AM Thread Starter
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Really need yíall a help

Tow haul light and no overdrive light comes on and off the abs light is either a LF Speed sensor or a speed sensor on the t-case. As u can see if very annoying to drive. Thankfully I live a lot closer to work than the normal person. Both wires are cut for the tow haul at the shifter so I donít see how itís getting told to be put into tow haul mode. I just bought this truck 3 hours away and of course it didnít do any of this until I get home. Just really hope I can figure this out. Iím hoping the overdrive light is something to do with the speed sensor being faulty and Iím pretty lost about the tow haul. Hereís a video I took a little while ago on my way to work.




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post #2 of 17 (permalink) Unread 09-03-2019, 09:23 AM
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I'm afraid you are in for some exploring. The tow/haul switch is a momentary contact switch. It connects a light blue wire from the BCM to ground. That means that anything that momentarily connects the light blue wire between the switch and the BCM to ground will act just like the switch itself. The transmission will toggle between tow and not tow.

You apparently have an intermittent grounding condition on that wire. You need to find where it is rubbed through and fix it.

Alternatively you could cut the wire at the BCM. The one you want is in connector C3 in socket B11. B11 is second from the end between two empty sockets. C3 is brown.

The BCM is mounted directly under the steering column. It has 4 connectors. Three are on the end and one is underneath. I think C3 is the right one on the end but I'm not sure.
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post #3 of 17 (permalink) Unread 09-03-2019, 09:33 AM Thread Starter
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Originally Posted by mizterwizard View Post
I'm afraid you are in for some exploring. The tow/haul switch is a momentary contact switch. It connects a light blue wire from the BCM to ground. That means that anything that momentarily connects the light blue wire between the switch and the BCM to ground will act just like the switch itself. The transmission will toggle between tow and not tow.



You apparently have an intermittent grounding condition on that wire. You need to find where it is rubbed through and fix it.



Alternatively you could cut the wire at the BCM. The one you want is in connector C3 in socket B11. B11 is second from the end between two empty sockets. C3 is brown.



The BCM is mounted directly under the steering column. It has 4 connectors. Three are on the end and one is underneath. I think C3 is the right one on the end but I'm not sure.


Ok I will check that out thanks for the info. Itís def acting like a loose or broken wire I just was just confused how with the wires to the button being cut. Thanks for clearing that up. Do u think the no overdrive light is related?


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post #4 of 17 (permalink) Unread 09-03-2019, 02:33 PM Thread Starter
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Got In my truck and closed the door and just the no overdrive light came on. So I kept opening and closing the door and it would come on and off as I did it...




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post #5 of 17 (permalink) Unread 09-03-2019, 03:48 PM Thread Starter
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Ok so I found the light blue wire coming from the connector for the button on the shifter. The ground wire is spliced into this peach colored wired that doesnít look like something gm would do but correct me if Iím wrong??

IMG_0882.jpg




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post #6 of 17 (permalink) Unread 09-03-2019, 03:50 PM Thread Starter
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IMG_0884.jpg


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post #7 of 17 (permalink) Unread 09-03-2019, 04:10 PM Thread Starter
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So for some reason who ever I bought this truck from had to put the horn on a button which is wired to the black/yellow and they had it grounded to one of the bolts mounting the lower metal shield on the column (which i accidentally ran over backing out of the garage ) and since I un grounded the horn both the tow haul and no overdrive light did NOT came on while I drove it about a mile. Idk how that would have anything to do with it but thatís the only thing I took off. The black/yellow wire is mounted right above the light blue wire for the tow haul into the module. IMG_0885.jpg


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post #8 of 17 (permalink) Unread 09-03-2019, 04:39 PM
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No that doesn't look quite factory but it looks better than most non-factory work. I haven't been able to find that wire so I don't know what it is supposed to be.

In the video I think it is making momentary contact every time you close the door so that it toggles between states. If you get the wiring right I think it will all be sorted out.

The black and white ground wire is supposed to go to a junction block in the IP relay block, then to a splice and finally to ground G203. However, the only wires I can find in that circuit are either black and white or solid black. I don't see any tan or peach colored wires.

I'd be tempted to cut the black and white wire out of the splice you show and give it a separate grounding point. Then see what happens.

I don't think there is a problem with G203 because there are 37 things that ground through it and if it had a problem you'd have more troubles than the tow/haul switch.

It looks to me like there are 3 tan wires coming together at the splice as well as the black and white one.
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post #9 of 17 (permalink) Unread 09-03-2019, 04:47 PM Thread Starter
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Originally Posted by mizterwizard View Post
No that doesn't look quite factory but it looks better than most non-factory work. I haven't been able to find that wire so I don't know what it is supposed to be.



In the video I think it is making momentary contact every time you close the door so that it toggles between states. If you get the wiring right I think it will all be sorted out.



The black and white ground wire is supposed to go to a junction block in the IP relay block, then to a splice and finally to ground G203. However, the only wires I can find in that circuit are either black and white or solid black. I don't see any tan or peach colored wires.



I'd be tempted to cut the black and white wire out of the splice you show and give it a separate grounding point. Then see what happens.



I don't think there is a problem with G203 because there are 37 things that ground through it and if it had a problem you'd have more troubles than the tow/haul switch.



It looks to me like there are 3 tan wires coming together at the splice as well as the black and white one.


That black and white wire goes to a aftermarket button for the horn I just cut that wire at the butt connector and removed the whole button for now. Iím going to replace the steering soon and figure out why they did that with the horn. I didnít try to follow the peach wire very far but I think IIRC It was going towards the clock spring area. Iíll have to double check that. Is there a good link for a schematic ur referring to for the wiring diagram under the dash?


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post #10 of 17 (permalink) Unread 09-03-2019, 04:52 PM Thread Starter
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Nvm black and white wire is going to tow haul connector not horn. Sorry about that I had them mixed up until I looked at the picture again

Where would u suggest I ground out the black and white wire once I get another shifter?


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Last edited by Jt89; 09-03-2019 at 04:55 PM.
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