Tow Mirror Lights

dallas251 · March 6, 2020

My local dealer just put a new set of tow mirrors on my 2020 Sierra SLE. The blinker lights on the back work, but I can’t get the front LED’s to light up. Anyone that have them know how they work? I’ve tried reverse and turning on the cargo lights.

This is the first set the dealer has seen and they didn’t know. I’m guessing it’s going to need to go back, but wanted to check with y’all first.

dallas251 · March 10, 2020

Anyone? Called the dealer and they told me those lights just won’t work... I think they’re probably wrong but want to confirm. They should come on with the cargo light button right?

Chrisd534 · March 10, 2020

If you switched from the regular mirrors to the tow mirrors theres a wiring harness you need to buy to make all those features work

dallas251 · March 10, 2020

If you switched from the regular mirrors to the tow mirrors theres a wiring harness you need to buy to make all those features work

Yeah they supposedly installed the new wiring harness.

Chrisd534 · March 10, 2020

There is good information in this thread. According to some, even if you have the correct harness your BCM might not have the pins for those functions in place

kdd · March 11, 2020

I had the dealer install the tow mirrors on my 2020 with NHT and they had to do a software update along with the new harness. All lights work, engage cargo lamps to get rear lights to work when in reverse.

dallas251 · March 11, 2020

I had the dealer install the tow mirrors on my 2020 with NHT and they had to do a software update along with the new harness. All lights work, engage cargo lamps to get rear lights to work when in reverse.

Thanks I just tried that, but no dice. It’s going back Thursday.

Just to clarify though, when you say “engage cargo lamps” which button are you pushing? The same one you use to turn on your bed lights? The below image shows the buttons I have. No fog lights or task light button which is different than higher trims. Maybe the task light button that I’m missing is the one that does it?

kdd · March 11, 2020

10 hours ago, dallas251 said:

Thanks I just tried that, but no dice. It’s going back Thursday.

Just to clarify though, when you say “engage cargo lamps” which button are you pushing? The same one you use to turn on your bed lights? The below image shows the buttons I have. No fog lights or task light button which is different than higher trims. Maybe the task light button that I’m missing is the one that does it?

Yes, the button that turns on your bed lights will activate the rearward tow mirror lights when truck is in reverse.

SamDSJR · March 13, 2020

Yeah they forgot to program them. When they bought the mirrors for you a code number came in the box on a sheet of paper. They have to use that to call GM and get the mirrors programed too. And as others have said you need harnesses too to make them work.

Edited March 13, 2020 by SamDSJR
Forgot info

Z45 · March 13, 2020

On 3/9/2020 at 11:41 PM, dallas251 said:

Yeah they supposedly installed the new wiring harness.

There are 2 wire harness's you need, rt and lt, if the truck did not come with that function. Those are another $200-$300, so I am told by local GM parts guy who said he called GMSO on it.

Bpgood1 · January 25, 2021

I have a 2021 trail boss lt, I did the tow .mirror install and the 2 harness swap today. I'm pleased to find that the turn signal/ amber running light features of the mirror work fine without dealer programming. The only negative is that the task lights do not work.

For my needs I dont imagine I'll spend the $125 to have them programmed just for task light function

JBradley9 · April 3, 2021

Bpgood1- Did you have to replace the wiring harness to? Im curios to know how you adjust both upper and lower mirrors with only the one button adjustment control inside ??? A new switch to? My dealer says they cant do it... thoughs?

Transient · April 7, 2021

Bpgood1- Did you have to replace the wiring harness to? Im curios to know how you adjust both upper and lower mirrors with only the one button adjustment control inside ??? A new switch to? My dealer says they cant do it... thoughs?

My 2020 Trail Boss LT came from the factory with tow mirrors. The lower mirrors are manually adjusted with your hand. The upper mirrors are power adjusted with the buttons on the door. For button remains the same. Things like power fold and power extend are what will change the door button controls.

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JBradley9 · April 7, 2021

Thats what I thought. Thanks

My truck has Lane Change Assist, dealer and Gm says Tow mirrors and on LCA truck will not work. After they sold me the truck with a mirror swap promise. I don't care if the LCA works on the tow mirrors, i know it cant. But can i not just do the harness swap and fire the code that comes with the mirrors and turn off LCA? Any info would be greatly appreciated
TIA

Transient · April 7, 2021

Thats what I thought. Thanks

My truck has Lane Change Assist, dealer and Gm says Tow mirrors and on LCA truck will not work. After they sold me the truck with a mirror swap promise. I don't care if the LCA works on the tow mirrors, i know it cant. But can i not just do the harness swap and fire the code that comes with the mirrors and turn off LCA? Any info would be greatly appreciated
TIA

You lose a lot of tech when going with tow mirrors, which is stupid. GM half-assed the tow mirrors. No reason to lose cameras, LCA, 360 view of they had done things right. Stupidly, it also eliminated from park sensors, front camera, and rearview mirror camera.

I'm not an expert on this, so take what I say with a grain of salt. Changing the mirrors and wire harness may also require a recalibration from GM to make things work properly. Having to get a recalibration every time I swap mirrors can be exhausting and expensive.

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