Reverse Lights and Backup Camera Not Working (Both OEM)

[Bkirch]

Hello all!

 

I have a 2018 GMC Sierra (SLE Double Cab 4WD) that I just bought out at the end of my lease. Love the truck! Unfortunately, at about 6 months and 200 miles out of my bumper-to-bumper warranty, I am having some electrical issues.

 

One night I fired up the truck and went to back out of the driveway and instead of seeing the video feed from my backup camera on the screen, I saw a blue screen (with the grid lines that follow my steering) and a message stating "service rear vision system." Not long after that, I noticed that my reverse lights are also not functioning.

 

There are two variables that have made this a little difficult to troubleshoot:

1.) My windshield was replaced in December due to a crack, and since then has been "repaired" for a leak at the top left corner 3 times.. I think the guy finally got it right this last time.. Fingers crossed.. Anyways, I had some water intrusion that dripped down the a-pillar and to the floor on the passenger side, so I do not know if/what this could have possibly damaged in the dash behind the glove box or elsewhere.

2.) After I bought the truck out from my lease, I decided to install subwoofers and an amplifier, so I have ran wires in the truck from front to back on both sides, the main power cable runs through the firewall and to the battery, and the signal wires run from the factory head unit using an interface that required no cutting or splicing of wires.

 

I have been looking for info in forums for a while and have tried what I could to chase out the issue. So far, I have verified that the issue with the camera and lights persists even with the new sound system disconnected. I have also disconnected the camera at the harness under the bed near the rear bumper to see if the reverse lights came back but they did not, so I don't believe the camera itself has gone bad. I have replaced the reverse lamp bulbs with new bulbs (tried LED and incandescent) and that did not change anything. I have replaced the engine compartment fuse box to verify that the internal relay on the PCB board that feeds power to the camera and reverse lights had not failed, but there was no change. Using a multimeter, I measure 135mV at the reverse light sockets, and at fuse #33 in the underwood fuse box when the reverse lights should be on.

 

My remaining thoughts are that I knicked a wire somewhere while wiring up my sound system, or that the BCM has gone bad. I have checked all BCM fuses and they are good. I still have yet to find the time to meter out the full circuit for the lights and camera, but that will likely be my next step, however I have not been able to find a great schematic on the wiring for either that identifies which wires/pins/harnesses to check. I have seen many forum posts regarding this issue, but none of the solutions others have posted have solved my problem yet. I am hoping someone out there may have an idea on what to check next, or perhaps a better schematic to follow than what I have been able to find so far.

 

Anyone have any ideas? Thanks in advance for any help!!!

 

Side note - I work for a company that does automotive crash testing work, and we do have some scanners at the shop - I plan to grab one and do some diagnosing that way soon, but I do not know what to look for exactly. If anyone has any insight on what to keep an eye out for let me know as well!

[JimCost2014]

37 minutes ago, Bkirch said:

Hello all!

 

I have a 2018 GMC Sierra (SLE Double Cab 4WD) that I just bought out at the end of my lease. Love the truck! Unfortunately, at about 6 months and 200 miles out of my bumper-to-bumper warranty, I am having some electrical issues.

 

One night I fired up the truck and went to back out of the driveway and instead of seeing the video feed from my backup camera on the screen, I saw a blue screen (with the grid lines that follow my steering) and a message stating "service rear vision system." Not long after that, I noticed that my reverse lights are also not functioning.

 

There are two variables that have made this a little difficult to troubleshoot:

1.) My windshield was replaced in December due to a crack, and since then has been "repaired" for a leak at the top left corner 3 times.. I think the guy finally got it right this last time.. Fingers crossed.. Anyways, I had some water intrusion that dripped down the a-pillar and to the floor on the passenger side, so I do not know if/what this could have possibly damaged in the dash behind the glove box or elsewhere.

2.) After I bought the truck out from my lease, I decided to install subwoofers and an amplifier, so I have ran wires in the truck from front to back on both sides, the main power cable runs through the firewall and to the battery, and the signal wires run from the factory head unit using an interface that required no cutting or splicing of wires.

 

I have been looking for info in forums for a while and have tried what I could to chase out the issue. So far, I have verified that the issue with the camera and lights persists even with the new sound system disconnected. I have also disconnected the camera at the harness under the bed near the rear bumper to see if the reverse lights came back but they did not, so I don't believe the camera itself has gone bad. I have replaced the reverse lamp bulbs with new bulbs (tried LED and incandescent) and that did not change anything. I have replaced the engine compartment fuse box to verify that the internal relay on the PCB board that feeds power to the camera and reverse lights had not failed, but there was no change. Using a multimeter, I measure 135mV at the reverse light sockets, and at fuse #33 in the underwood fuse box when the reverse lights should be on.

 

My remaining thoughts are that I knicked a wire somewhere while wiring up my sound system, or that the BCM has gone bad. I have checked all BCM fuses and they are good. I still have yet to find the time to meter out the full circuit for the lights and camera, but that will likely be my next step, however I have not been able to find a great schematic on the wiring for either that identifies which wires/pins/harnesses to check. I have seen many forum posts regarding this issue, but none of the solutions others have posted have solved my problem yet. I am hoping someone out there may have an idea on what to check next, or perhaps a better schematic to follow than what I have been able to find so far.

 

Anyone have any ideas? Thanks in advance for any help!!!

 

Side note - I work for a company that does automotive crash testing work, and we do have some scanners at the shop - I plan to grab one and do some diagnosing that way soon, but I do not know what to look for exactly. If anyone has any insight on what to keep an eye out for let me know as well!

Welcome to the site.

 

Original battery?

[FauxCE]

Hello BKirch,

I am interested to see what your scanners turn up. I have been without reverse lights/camera for ~6mo now and have had the same things happen as you described. No additional audio equipment here and no recent windshield replacement (~18/24 mo ago) so I think you are probably safe there. In my researching I think that the connections from front to back runs from a box behind lower glove box referred to as an HMI box down to the frame on the passenger side, along the frame to the back of the truck, over to a collection of harnesses on driver & bumper side of spare tire, and then splits to  lights/trailer harness/camera. My fuses all check out as well and I have unplugged/replugged in each of the harnesses to see if anything changes but no dice. I've wired up some spare pod lights under my bumper and hooked them into the trailer harness to serve as reverse lights until I find a fix. I have read about camera failures where the HMI box needed to be replaced as well as just the camera needed to be replaced but none also lost reverse light functions. 

[Bkirch]

On 3/31/2022 at 11:37 PM, JimCost2014 said:

Welcome to the site.

 

Original battery?

Hi Jim, thanks!

 

Sorry for the delayed reply, yes it is the original battery and voltage looks good on it with truck running or off. 

[Bkirch]

3 hours ago, FauxCE said:

Hello BKirch,

I am interested to see what your scanners turn up. I have been without reverse lights/camera for ~6mo now and have had the same things happen as you described. No additional audio equipment here and no recent windshield replacement (~18/24 mo ago) so I think you are probably safe there. In my researching I think that the connections from front to back runs from a box behind lower glove box referred to as an HMI box down to the frame on the passenger side, along the frame to the back of the truck, over to a collection of harnesses on driver & bumper side of spare tire, and then splits to  lights/trailer harness/camera. My fuses all check out as well and I have unplugged/replugged in each of the harnesses to see if anything changes but no dice. I've wired up some spare pod lights under my bumper and hooked them into the trailer harness to serve as reverse lights until I find a fix. I have read about camera failures where the HMI box needed to be replaced as well as just the camera needed to be replaced but none also lost reverse light functions. 

Hi Faux!

 

Unfortunately I am still dealing with the issue. Scanned the truck at work and pulled a B127B which gives a little bit of helpful info. 

 

I talked to a tech at a local dealership and he mentioned the HMI box as well, but he didn't believe that the HMI or a faulty camera should take out the reverse lights as well. I pulled the plug on the camera to see if it was malfunctioning and pulling the whole circuit down but the reverse lights still did not work and I had the same blue screen and error message in the truck. I also pulled out the HMI box and it did not appear to have taken on any water or be damaged or fried, but unfortunately I don't have the equipment to test that sucker any further. With the skepticism of the GM tech, I am reluctant to throw money at a new HMI, but that may be one of my next steps.

 

I'm also starting to question the fuse box thought again - the one I replaced mine with was a used box I purchased on eBay, so it could be just my luck that I got another one with the same PCB board relay bad.. If it's not that or the HMI, I'm starting to wonder if it could be the BCM, but I'm also reluctant to throw money at a new one of those.. It may be time to just bite the bullet and take it to the dealership for a proper diagnosis.

 

I'll keep you posted if I have any new discoveries!

[Abdulrehman]

Following this.

 

I also have same issue but my backup camera + reverse light works sometimes so i dont know from where should i start diagnosing

 

 

[14LTZ-1LZ]

Check the junction box behind the spare tire. Your rear camera, reverse light and trailer connection goes through this junction box. 

[USN24]

2018 GMC Sierra 1500 V-6, reverse lights are always on even when the truck is turned off and the key removed and the back up camera is on while driving both forward and reverse.  I got the reverse lights to go out by pulling fuse 33 from the under hood fuse block.  Wondering if you have found the problem on yours which might point me in a certain direction.

[USN24]

2018 GMC Sierra 1500 V-6, reverse lights are always on even when the truck is turned off and the key removed and the back up camera is on while driving both forward and reverse.  I got the reverse lights to go out by pulling fuse 33 from the under hood fuse block.  Wondering if you have found the problem on yours which might point me in a certain direction.  This is my daughters truck, she just bought it used about a month ago.  This is the first big issue she has had with the truck

Edited April 30, 2022 by USN24
added more info.

[FauxCE]

Might have found a fix, and discovered another problem. I called myself checking all the relevant fuses first time around but alas after checking them again fuse 33 (thanks USN24) in my engine fuse box "Reverse Lamps" was blown. Little mini 10A. Popped in a spare and voila I've got my reverse camera and back up lights again!

 

But now the problem. The camera looks like I'm taking a shower and trying to look out the shower door! HAZY is an understatement. I wiped it off and it got a little clearer but I fear a replacement camera is in my future. I'll try to clean it up better in the next few days when I get a minute but if not I'll probably get a new camera in the next few months. 

Edited May 3, 2022 by FauxCE
To credit USN24

[Bkirch]

So after striking out with everything I have tried so far, I decided to order a replacement camera for the truck and see if it would do anything before taking it in to the dealer.. Amazon Prime with free returns, so I figured I had nothing to lose. As soon as I swapped the new camera in it began working instantly, but my reverse lamps still do not work. I was so sure the two malfunctions were related, but it turns out they may not have been. Now that the camera is replaced, I just have one simple circuit to troubleshoot.

 

For those of you who mentioned similar issues, don't write off a bad camera as a possible issue. It took 10-20 minutes to swap out, and at least in my case, it eliminated a number of other possible (and more expensive) issues. 

[FauxCE]

13 hours ago, Bkirch said:

 order a replacement camera 

Did you go OEM or step up resolution? Also if stepped up resolution was the screen capable of showing an improved picture or was a higher resolution camera bottlenecked by the screen?

[Abdulrehman]

On 5/3/2022 at 11:25 PM, FauxCE said:

Might have found a fix, and discovered another problem. I called myself checking all the relevant fuses first time around but alas after checking them again fuse 33 (thanks USN24) in my engine fuse box "Reverse Lamps" was blown. Little mini 10A. Popped in a spare and voila I've got my reverse camera and back up lights again!

 

But now the problem. The camera looks like I'm taking a shower and trying to look out the shower door! HAZY is an understatement. I wiped it off and it got a little clearer but I fear a replacement camera is in my future. I'll try to clean it up better in the next few days when I get a minute but if not I'll probably get a new camera in the next few months. 

I dont think so because for me it works sometime and sometime it dont no idea whats the problem dropped the car in GMC they told me to replace the fusebox in engine  bay i highly doubt that still looking for answer

 

any help appreciated

[Full Throttle Gaming XP]

Hello,

 

I've had the same issue as the OP. Has anyone figured out this issue?