2020 AT4 HD parking sensors and blind spot not working

Wellarmedlamb · April 16, 2023

I just picked up a 2020 AT4 HD Dmax and I get two messages on startup.

Service Park Assist System

Service Side Detection System

Neither system works at all.

Any advice on what to look for would be appreciated.

Dr1ft3r · April 16, 2023

3 hours ago, Wellarmedlamb said:

I just picked up a 2020 AT4 HD Dmax and I get two messages on startup.

Service Park Assist System

Service Side Detection System

Neither system works at all.

Any advice on what to look for would be appreciated.

I just had my front and rear bumpers swapped out for Ranch Hand bumpers. I also had that message about the side detection system when I started my truck when I was about to leave. I told the installers and they had forgot to plug the wire harness back onto the blind spot monitor sensors.

So my guess is either the sensors are not connected to the wire harness, the wire harness is not connected to the cpu, or the wire harness is damaged in some way.

Edit: Maybe a sensor is not working either? But for both systems to not be working then I'd guess it would have to be at least 1 sensor from each system, which seems less likely. With my issue I did not get a message about the park assist system.

Check the connections and if that doesn't fix the issue I would go to the dealer.

Edited April 16, 2023 by Dr1ft3r

Wellarmedlamb · April 17, 2023

6 hours ago, Dr1ft3r said:

I just had my front and rear bumpers swapped out for Ranch Hand bumpers. I also had that message about the side detection system when I started my truck when I was about to leave. I told the installers and they had forgot to plug the wire harness back onto the blind spot monitor sensors.

So my guess is either the sensors are not connected to the wire harness, the wire harness is not connected to the cpu, or the wire harness is damaged in some way.

Edit: Maybe a sensor is not working either? But for both systems to not be working then I'd guess it would have to be at least 1 sensor from each system, which seems less likely. With my issue I did not get a message about the park assist system.

Check the connections and if that doesn't fix the issue I would go to the dealer.

Thanks! Great info. Where are the blind spot sensors located?

Dr1ft3r · April 17, 2023

45 minutes ago, Wellarmedlamb said:

Thanks! Great info. Where are the blind spot sensors located?

Behind the back of the steps on the corners of your rear bumper. You can't see them from the outside. The step material must allow them to detect objects through them. If you get under the truck and look up behind the bumper you should be able to see them, or the wire harness that connects to them.

GMCustomerService · April 26, 2023

On 4/16/2023 at 12:26 PM, Wellarmedlamb said:

I just picked up a 2020 AT4 HD Dmax and I get two messages on startup.

Service Park Assist System

Service Side Detection System

Neither system works at all.

Any advice on what to look for would be appreciated.

This is certainly not what we like to hear, Wellarmedlamb. Please know, customer satisfaction is extremely important to us. Our team would be more than happy to take a closer look into the concerns with your 2020 GMC Sierra AT4. To do so, please send an email to [email protected] with ATTN: Wellarmedlamb/GM Trucks in the subject line.

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