2015 f350 CCSB Lariat 4x4 6.7 diesel, 87k miles. Bought it used last winter. Body is stock except for an aftermarket 5th wheel tailgate. Stock security system.

As the title says, I'm having issues with the alarm occasionally going off for no reason. I have not seen any random hood ajar or door ajar messages. A lot of the stuff I've found online says the hood latch is a common source of this problem, but IDK if that's my issue. My hood latch looks different from all the ones I've seen on YouTube. I don't even see a wiring harness connector on it. I know it has a hood sensor, but I don't know where the wires for it are located. I don't want to just throw a new hood latch at it and hope that fixes it.

I'm wondering what my options are for diagnosing. I have a bluetooth OBD II dongle and Car Scanner app on my phone, but it doesn't appear to show alarm sensor data (at least not that I could find). I'd have to buy a laptop and OBDLink adapter if I wanted to use Forscan. So $70 for the adapter and $180 for the cheapest laptop at Walmart, $250-ish all in. Not sure what my local Ford dealer charges for diagnostics, but I'm guessing a similar amount. Is there any other way to diagnose this issue?

Is the aftermarket tailgate a possible culprit? Not sure if there is a security sensor for the tailgate.

I've also heard people say they've changed their security settings to "perimeter only" in case there's a bug flying around inside setting off the motion detectors. I'm not finding where to do that in my gauge cluster. Can anyone point me in the right direction?

Thanks much.

 

Not sure on the sensors, though an aftermarket 5th wheel tailgate COULD cause issues, especially if the power tailgate lock connector wasn't properly covered when the tailgate was removed.

To set your security settings to 'perimeter only,' I THINK you can change that in the settings through the radio (not gauge cluster), otherwise every time you shut the truck off a screen should pop up with the selection of 'perimeter only' or 'all sensors.' Side note, if your teenager wants to sit in the back seat while you run inside real quick, make sure to set it to 'perimeter only' or it WILL set the alarm off if he moves.

 

In case anyone else is dealing with this issue, here's my temporary work-around until I can get the issue fixed:


According to my manual, the alarm is armed any time the doors are locked electronically (either using the fob or using the lock button on the door), so if you lock it from outside using the key, the alarm should not be armed. You have to have your unlock strategy set to two stage unlock, which can be done via the vehicle menu on the gauge cluster.

Be aware that your alarm is not set when you do this, so you are vulnerable to a break-in.

After doing a little more online searching on how to actually fix the problem, I'm pretty sure I'm going to have to either take it to a dealer or get the stuff I need to use Forscan to diagnose it. Otherwise it's just a guessing game.

 

I had this problem on my 2012 6.2L XLT. It ended up being the hood switch, like you I was beginning to think I needed some diagnostic equipment or it was going to be a Dealer diagnostic to find the problem. I finally found a thread stating that if you lock the vehicle with the key fob by pushing the lock button twice in a row and the horn honks twice it means the system detects a hood or door ajar. Which mine was doing, the hood switch on the 6.2L is located on the left side of the engine bay near the air filter. It sticks straight up with a black rubber boot over top of the plunger. I disconnected the switch and installed a jumper wire into the switch connector and locked the doors with the key fob. The horn didn't honk, and the alarm hasn't gone off randomly since. I'm not sure if you have a tailgate sensor being a lariat, I know mine does not.

 

I ended up taking it to the dealer. They diagnosed and repaired for $209 including tax, so not too terrible. It was indeed the hood ajar sensor. They diagnosed it using their scan software, which indicated that sensor was responsible for the last several alarms. $30 part, 150 labor, plus shop fee, tax, etc.

I asked the service advisor where that sensor is located since I could not find anything electronic-looking on the actual hood latch. He said it's off to the side - I haven't looked yet, need to get in there and see if I can find it for future reference.

If I had the proper scan equipment, I could have done it myself for less. But I just didn't have time to mess with it this week, nor the time to wait on the new OBDII adapter to be delivered. And the wife wasn't crazy about spending another 250 on more "stuff for the truck" right now.

 

So the hood sensor on my truck is located in front of the driver's side battery, next to the upper radiator hose. Easy to reach, would have been super easy to replace. Now I'm not feeling so great about $150 of labor for something that probably took half an hour to diagnose and replace. But I still paid less than it would have cost me to get up to speed on diagnosing this stuff.

 

Looks like they charged you an hours worth of labor, unless they’re higher than I think and that’s only 1/2 hr. No doubt that hood switch can be replaced in about 10 minutes max. Glad it’s fixed. Mine is in the same location. I was able to diagnose mine without any tools just by using the lock button on the key and listening to how the horn honked when the doors locked. Then I jumped the connector at that switch and the horn didn’t sound, knew that was my problem.

 

My '16' @ 81k miles has started this random alarm.I'll get the sensor and replace.

 

Changed the hood latch sensor today. Maybe this is why might have been setting the alarm off? It sortof fell apart.






New one installed.

 

That absolutely would cause the issue if it lost connection - it would presume the hood is being opened and set off the alarm.

 

Well the hood latch sensor and changing the battery in the key fob didn't stop the random alarm going off.

More sleuthing is needed.

I wonder if changing all the bulbs to led is possibly causing this somehow. I did change the mirror turn/ running and all the lights in the back (brake, running, reverse) to led bulbs. I guess I'll change them back and see what happens.

 

Doing a quick search came up with this.....

 

Gotta love all the touchy electronics on modern vehicles.

 

Maybe, just maybe it's fixed. The front passenger door ajar started showing on the dash even though the door was shut tight. $26 for the new sensor, 45 minutes and the dash warning is gone. So far the alarm hasn't gone off. We'll see if it can make it a day.

 

Hope that's it!