Horn Will Not Turn Off

[wspinks13]

Hello , very new to this group but would love some help with my truck. Have a 2018 Chevy Silverado 1500 LTZ and for several weeks now when locking the truck with the key fob sometimes the horn would sound when locking , sometimes sound very muffled or sometimes truck would lock with not horn chirp at all. So this evening went out to truck to get something out , unlocked with key fob, shut the door and hit the lock button and when the lights blinked to lock  the truck instead of the horn chirp , the horn actually just turned on full blast as if I were behind the wheel just laying on the horn. So I immediately hit the button on the key fob to unlock truck, hit the panic button , opened the doors and NOTHING I did would make the horn stop and was it was just stuck on. I then proceeded to go into action and popped the hood and disconnected the negative battery terminal to kill power. I let the truck sit for like 10 min and tried to re-connect the battery and as soon as I touched the terminal the horn would just go to full blast mode again. Then I just found the fuse to the horn under hood in fuse box and pulled the fuse and then horn shut off. 
 

Sorry for the lengthy testimony, lol but does anyone have any idea why the horn would be stuck in that On mode and will not turn off unless you pull the fuse? 
 

thanks ! 

[JimCost2014]

4 minutes ago, wspinks13 said:

Hello , very new to this group but would love some help with my truck. Have a 2018 Chevy Silverado 1500 LTZ and for several weeks now when locking the truck with the key fob sometimes the horn would sound when locking , sometimes sound very muffled or sometimes truck would lock with not horn chirp at all. So this evening went out to truck to get something out , unlocked with key fob, shut the door and hit the lock button and when the lights blinked to lock  the truck instead of the horn chirp , the horn actually just turned on full blast as if I were behind the wheel just laying on the horn. So I immediately hit the button on the key fob to unlock truck, hit the panic button , opened the doors and NOTHING I did would make the horn stop and was it was just stuck on. I then proceeded to go into action and popped the hood and disconnected the negative battery terminal to kill power. I let the truck sit for like 10 min and tried to re-connect the battery and as soon as I touched the terminal the horn would just go to full blast mode again. Then I just found the fuse to the horn under hood in fuse box and pulled the fuse and then horn shut off. 
 

Sorry for the lengthy testimony, lol but does anyone have any idea why the horn would be stuck in that On mode and will not turn off unless you pull the fuse? 
 

thanks ! 

Welcome to the site.

 

My first guess is if you have the original battery, it is probably telling you that it is going bad.

 

Most other replies are going to be centered on a bad ground, or bad battery cable as they seem to be the most common issues with electrical problems in the K2's. 

 

[kickass audio]

do you have anything aftermarket for a remote start? Some idiot (me) didn't pay attention to the wire polarity of my rear defroster and when I triggered it to work from the aftermarket remote start it didn't warm my mirrors so I pressed the button on the dash and it shorted the aftermarket remote start and would not let the truck shut off and the horn was blasting non stop until I blew one of the two horns.

 

I ended up having to disconnect the aftermarket remote start and replaced the blown part on it but just last weekend gave up on the aftermarket remote start since it randomly sets off my alarm for no reason.

 

What I would suggest would be to unplug the horn and test power on the wire harness. I am fairly certain the +12v should be live at all times and the ground will ground out when the horn is called to run since GM usually loves to switch the grounds and leave the hot wires on. If it doesn't have continuity on one of the two wires then that would tell me that the BCM that controls the horn and the horn switch in the wheel is fine and your horns itself is probably faulty. Otherwise if the wires are live at all times then you need to find where the short exists, whether a wire was chewed up and is making contact somewhere along the way or something else.

[M1ck3y]

To turn the horn off I think you have to press the unlock button, then hit the lock button twice (whatever it is, its in the manual). You can also start the vehicle to turn the alarm off. 

 

Are you sure you didn't hit the panic button?

Edited November 13, 2021 by M1ck3y

[wspinks13]

1 hour ago, JimCost2014 said:

Welcome to the site.

 

My first guess is if you have the original battery, it is probably telling you that it is going bad.

 

Most other replies are going to be centered on a bad ground, or bad battery cable as they seem to be the most common issues with electrical problems in the K2's. 

thanks for response, but the battery was replaced with a factory AC Delco just last month. All battery cables are in perfect condition! 

 

[wspinks13]

Truck has factory remote start and no after market accessories installed on truck. I will definitely run some test check power running to horn. All wires look to be in perfect condition leaning to a faulty horn.

[Mr. Z71]

Someone correct me if I’m wrong, but I assume that due to the current draw of a horn, or horns (dual setup), a relay is required. I could find nothing in the owner’s manual referencing a horn relay or location of one, but shouldn’t the possibility of the relay contacts being stuck (welded together) be considered. Sure is what it sounds like to me. Again, I’m assuming that even the newer vehicles require a relay due to current requirements just as older ones do.

[mjm-1957]

The horn relay is internal to the underhood fuse block. If the wiring checks out and the air bag is good, than the relay may be shorted and keeping the horns on.

[Mr. Z71]

Thanks for clarifying this, I learned something. So if the relay fails you have to replace the fuse/junction block, correct? Who signed off on a design such as this?

[mjm-1957]

Welcome to GM. I have a stack of bad fuse boxes under my bench for all sorts of problems. I keep them for all the fuses and relays as spares.The high speed wiper relay  is also internal and goes bad quite often. That fuse box is not cheap either.

[M1ck3y]

Where were your trucks made?

[MikeBMW]

20 hours ago, M1ck3y said:

Where were your trucks made?

From the Wiki:
"The GMT K2XX products [were] produced at four GM assembly plants: Arlington (all SUVs), Flint (double and crew cab heavy-duty pickups), and Fort Wayne (regular and double cab light- and heavy-duty pickups) in the United States, along with Silao Assembly in Mexico for the crew cab light duty pickups. "

Edited November 17, 2021 by MikeBMW

[Salcon]

[I have a 2014, but I suspect the pin locations and colours are the same for a 2017]

 

The horn on these K2 trucks is fairly straight forward. The steering wheel button signal goes through the clockspring, and feeds a ground signal into the Body Control Module (BCM Green connector, pin 18, wire colour Green/White) when the horn button is pressed.

 

The BCM outputs a switched ground to the horn relay inside the underhood fuse box (BCM Brown connector, pin 19, wire colour Brown/White).

 

Inside the fuse box, the horn relay coil has one side connected to B+, and the other to the BCM control. With the switch contacts, one side is tied to B+, the output is through fuse 48 and to the horn(s).

 

The real question, is if you have a bad relay, or worse... bad BCM output.

 

You can do a simple test - With the keys out of the ignition, unplug the brown connector from the BCM. The BCM is right behind the floor brake pedal, its a black box with 7 coloured connectors.

With the brown connector unplugged, reinstall your horn fuse, F48.

IF your horn still blares non-stop, you most likely have a bad relay. If the horn does not blast, you could have a bad BCM output, or, you could have a bad clockspring/horn button.

 

You can do some pinpoint tests too. Pull fuse 48, reconnect any BCM connectors you unplugged, and reconnect your battery.

Measuring voltage to ground, measure the brown/white wire as well as the green/white wires previously mentioned. You should have close to 12 volts normally with horn button not pressed. When you press and hold the horn button, you should see those drop to near zero. They should return to around 12 volts when you let off the horn button. If so, this means your horn button and BCM output are working correctly, and you have a bad horn relay.

 

If the green/white wire stays zero all the time, disconnect the green connector from BCM and measure resistance to ground on green/white wire. If this is near zero ohms regardless if horn button is pressed or not, you have a bad button, clockspring, or a short to ground somewhere.

 

Most likely though, you will find you have a bad internal horn relay. It is a circuit board mounted relay. If your BCM output is working as intended, and you want to save some cash and not replace the fuse block, you can keep fuse 48 removed, and add your own relay. Just a matter of tapping the brown/white wire at the BCM (this is easier then at the fuse block, but you can do it there too), and tapping the horn feed. 4 pin relay, and 2 fuse holders will do. 2 or 3 amp for the relay coil, and 15A for the horn output. You will want to of course, make sure you buy a relay socket that has a  protection diode (and mind the polarity applied to coil), else you could spike your BCM. The BCM likely already has spike protection, but still good to be on the safe side.

 

Considering what you described, before the horn fully failed in the on position, it sounds like your horn relay switch contacts were going bad and in the last straw they got stuck together.

 

EDIT - And if you are feeling really adventurous, the horn relay can be replaced. It is tedious to open the fuse block, but totally doable. Relay is an F&T Fujitsu FTR-P3AN012W1.

Edited November 19, 2021 by Salcon

[Doc_derek]

 Codos to Salcon for a well explained test procedure. Being an old-timer, I’d somewhat diagnosed the problem, but Saltos helped me to diagnose with certainty.

My stuck horn problem started with intermittent operation when locking my 2015 Chevy Silverado LTZ. It would sound some times, then would not at others, until it stoped sounding altogether.

One evening while waiting in line for gas at Costco, a pump became available, but the person in front of me was asleep at the wheel. In an attempt to awaken them, I pressed on my horn. This is the time it chose to not shut off (embarrassing).

Not knowing the location of the horn fuse, I preceded to drive home (approx. 2 miles), with the horn blaring. By the time I reached home, the horn had stopped. I could hear the sound slowly decreasing, until going dim permanently.

In my testing, I found there was a constant 12 volts at the horn connector, indicating I had a faulty horn relay (constant 12 volts at horn connector), and a bad horn (no sound although 12 volts present at horn connector).

The horn relay is built into the under-hood fuse box, which cost $180 from Chevy dealership. The horn was about $20 on Amazon.

Replacement of the fuse box was relatively easy. Instructions can be found on internet. The horn was as easy Access to the bolt required loosening the computer module and windshield washer reservoir. Even doing so required working in tight spaces, but perseverance got it done.

Horn working again, now on the the faulty passenger-side power mirror (not folding).
 

[fyrfytr2223]

On 11/12/2021 at 8:56 PM, wspinks13 said:

Hello , very new to this group but would love some help with my truck. Have a 2018 Chevy Silverado 1500 LTZ and for several weeks now when locking the truck with the key fob sometimes the horn would sound when locking , sometimes sound very muffled or sometimes truck would lock with not horn chirp at all. So this evening went out to truck to get something out , unlocked with key fob, shut the door and hit the lock button and when the lights blinked to lock  the truck instead of the horn chirp , the horn actually just turned on full blast as if I were behind the wheel just laying on the horn. So I immediately hit the button on the key fob to unlock truck, hit the panic button , opened the doors and NOTHING I did would make the horn stop and was it was just stuck on. I then proceeded to go into action and popped the hood and disconnected the negative battery terminal to kill power. I let the truck sit for like 10 min and tried to re-connect the battery and as soon as I touched the terminal the horn would just go to full blast mode again. Then I just found the fuse to the horn under hood in fuse box and pulled the fuse and then horn shut off. 
 

Sorry for the lengthy testimony, lol but does anyone have any idea why the horn would be stuck in that On mode and will not turn off unless you pull the fuse? 
 

thanks ! 

I have a similar situation going on, I see you had this happen over 18 months ago.

Did you you ever get it resolved?

What was the final outcome/ reason the horn would not shut off?