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Discussion Starter · #1 · (Edited)
I’m not sure what is the problem, but my truck has done this since to drive it off the lot. Has anyone seen this issue?

My rear park assist is showing off. It shows the message pretty much every time I start driving from a stop - traffic lights, stop signs, etc.

Today I snapped a picture. I’m about 2’ off the rear garage wall, with Park Assist enabled and turned on, and in reverse. By all accounts, my safety alert sear should be going apeshit at this point and I should have hazard triangles on the rear camera screen.

Any ideas? I have checked for DTCs, but there are none. I’m at a loss.

1091620


1091621
 

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An off message won’t store any dtcs not to mention that if you don’t have a high end diagnostic tool, you won’t be able to access the module that stores dtcs for the park assist system. You really need to have the dealer look at the disable history data for the system to get a better idea of what the system is seeing that it doesn’t like.
 

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2021 Silverado 2500HD LTZ L5P
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Do you have a large hitch in the coupler?? My 2021 ltz does it with my gen-y hitch in but not when I have it out. My understanding is, it is supposed to disable when it senses what it thinks is a trailer behind you. But I could be wrong.

I drive around with the hitch in when not towing because people in wisconsin love to tailgate but back way off when they see that ridiculous hitch. Works in parking lots too. None of those ding dongs like to be close to it
 

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Discussion Starter · #4 ·
Nope, no hitches are installed unless I'm towing. I have the Multi-Pro tailgate and to avoid damage, I only have a hitch installed if I'm towing.

There is an option for Park Assist enabled with the tow bar setting. I've made sure that I'm not using that selection.
 

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2021 GMC AT4 3500 CC LB
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What you describe sounds just like a dirty sensor. I am sure you already explored this possibility.. so I would assume bad sensor. My initial 2 cent.
 

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2019 LTZ
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My 2019 has had the same exact issue. Been to 2 different dealerships and they are blaming the front cattle guard for my “rear” sensors turning off ..😡
 

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You need to enable the park assist with tow bar. It’ll keep sensors working with hitch in receiver
 

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2019 LTZ
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What you describe sounds just like a dirty sensor. I am sure you already explored this possibility.. so I would assume bad sensor. My initial 2 cent.
I asked both dealerships about that possibility and they disagreed….
 

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My 2019 has had the same exact issue. Been to 2 different dealerships and they are blaming the front cattle guard for my “rear” sensors turning off ..😡
I am guessing that you have the UD5 (front and rear) system and not just the UD7 (rear only) system and have seen specifically just a “rear park assist off” message?

If you block the front sensors with tape, do you get a front park assist off message?

Did the dealer show you the park assist system disable data, on the scan tool, showing you this?
 

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I asked both dealerships about that possibility and they disagreed….
A dirty/damaged sensor can most definitely turn the system off. Also damage to the bumper near the sensors or even too thick of paint (if they are painted to match the bumper) can cause issues.
 

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Discussion Starter · #11 ·
What you describe sounds just like a dirty sensor. I am sure you already explored this possibility.. so I would assume bad sensor. My initial 2 cent.
They're definitely not dirty, but that does raise a good reminder. I've encountered the same before on my 2020 2500 AT4 in the winter when ice/snow buildup occurs on the front sensors.

You need to enable the park assist with tow bar. It’ll keep sensors working with hitch in receiver
In my case, I don't think this is the case. I don't ever keep a hitch installed.

I am guessing that you have the UD5 (front and rear) system and not just the UD7 (rear only) system and have seen specifically just a “rear park assist off” message?

If you block the front sensors with tape, do you get a front park assist off message?

Did the dealer show you the park assist system disable data, on the scan tool, showing you this?
I do have the UD5 option for front and rear. I ordered my truck in Feb 2021 and took delivery on 4/20/21. It's got every option and package, as my order/build went thru before features were being removed and constraints went into place.

I haven't tried blocking off the fronts, but so far there has never been a warning on the DIC for the fronts. I'll have to give it a try later today.

At this time, I haven't been able to have the truck looked at by the dealer yet.

A dirty/damaged sensor can most definitely turn the system off. Also damage to the bumper near the sensors or even too thick of paint (if they are painted to match the bumper) can cause issues.
Yup, and I've seen this before on my 2020 2500 AT4 - particularly the fronts when covered in snow/ice buildup.

They are painted to match, but this is a factory feature for the AT4. Not saying I disagree, just that the paint is OEM. And the rear bumper has no damage.
 

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Discussion Starter · #12 ·
Last evening I hopped on the creeper and looked at the sensor plugs in the rear bumper. It's a tight squeeze, but I did re-seat the connectors on the sensors. I didn't expect much but figured it was worth a shot.

Afterwards, I started the truck and put it in reverse - and RPA worked without issue. The safety alert seat was vibrating and I had the hazard triangles on the backup camera screen. I didn't go for a drive, but I did pull out of the garage and back in again. RPA continued to work.

I'll be paying closer attention to this and if the 'Rear Park Assist Off' message comes back on the DIC, I'll have this looked at by the dealer.

Since it's only a convenience feature, I'll probably wait until the next service visit.

Thanks to all for the help so far. Any other advice/feedback is appreciated!
 

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2019 LTZ
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I am guessing that you have the UD5 (front and rear) system and not just the UD7 (rear only) system and have seen specifically just a “rear park assist off” message?

If you block the front sensors with tape, do you get a front park assist off message?

Did the dealer show you the park assist system disable data, on the scan tool, showing you this?
I was never shown anything from either dealership. I have both front & rear sensors. I turn the park assist on ( I normally always leave it turned on) and it will just automatically turn off after I start down the road ( at different time intervals). Sometimes it stays on for longer periods of time before turning off.
 
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2021 High Country 3500HD DRW Crew Cab LB
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Taking my 2021 High Country 3500HD in for this problem on the Sept. 13th. I will see what happens.
 
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