I am dealing with an issue with my alarm system/immobilizer that has been randomly occurring for a few months but has happened for 5 consecutive days. It seems like it is happening when it is cold, usually at 05:30 in the morning when going to work but it was exhibiting the same symptoms Sunday at 09:00 as it was 42 degrees. The alarm system does not honk when unlocking/locking the car, either with the key fob or by using the door sensor. The car starts fine and the voltage on the battery is 12.46 tested with a Fluke multimeter. The immobilizer light is not on during this period of time while driving, and when pressing the lock button when outside the vehicle, the immobilizer light on the dash is slowly flashing.




When driving, as the temperature increases or as I am now accelerating to 60 mph+, when I am running across items on the road like lane reflectors, the motion sensor of the alarm system starts triggering (3 short beeps). It starts intermittently, then starts becoming more frequent, until my alarm system fully triggers (car starts honking, lights flashing). The car is drivable during this period of time (immobilizer does not shut off the ignition). The way to stop this is to drive while the alarm is going off for about a minute or two, or to pull over, shut off the car, and push the unlock button on the key fob (the alarm system now does the two short honks as under normal operation). I have driven all the way to work like this before, where the alarm system is seemingly no longer active, shut off the car and opened the door, which triggered the alarm. This means that the alarm is NOT being disabled in the morning and is dormant for some reason until either the temperature is higher under the hood, or until I am reaching a higher speed. I did notice this morning that the blue light under the steering wheel was flashing when the alarm issues started, but did not notice if it was flashing to begin with. I will check tomorrow when the issues starts up again. The key fob also has good range as I recently replaced the battery.




I am guessing that the alarm wiring may be damaged and potentially has condensation which then dries off as the car warms up, but the car alarm does not randomly go off at all, and the beep portion of the alarm system works perfectly fine. Really strange and troublesome. Has anyone dealt with this issue, or have any ideas?

 

The owner's manual should have information on how the lights behave on the security/door lock system. You'll want to learn what the various lights indicate

The immobilizer system is a seperate security system that allows a programmed key (or key fob if you have a push start). The indicator would be a green key on the instrument cluster

Acting up in cold temps points toward an electrical/sensor issue. Battery voltage is easy to test with a meter. First test the battery voltage with the car running. You should read over 13.3V. Your 12.5 V result can be misleading if the battery wasn't under load. The battery will have a surface charge that reads good on your meter, but you still could have a bad battery. You can turn on the headlights to load the battery with the engine off. If you drop to 10.4 V or 8.2V immedately, you have 1 or 2 dead cells.

Alternatively, you can stop by a parts store and have them do the battery/starter/alternator check. They can also scan for codes. The codes might give you some direction if the battery isn't causing these symptoms.

 

Thanks for the reply, I will test the voltage off/lights/on this afternoon and in the morning for comparison, and rescan with the Autel. Last time I checked there were no codes, but it can’t hurt to check again. I will post my findings tomorrow to reduce clutter.

unfortunately, the manual was pretty unhelpful regarding the security system.

edit- forgot to add, the battery is only about a year old and AGM, so honestly not expecting it to be the culprit, but not willing to assume that it is not. Will be testing it.

Edit 2 - Ancel AD310, not Autel

 

To update the situation, I scanned the car for codes and I tested the battery as recommended in three states: engine off, engine off with lights on, and engine on. I took two sets of readings below:01/21/25 17:15

• Off - 12.46
• Lights - 12.33
• On - 14.5
• OBDII codes (Ancel AD310) - none

01/22/25 05:20

• Off - 12.33
• Lights - 12.13
• On - 14.52
• OBDII codes - none

based on the results, I would like to rule out the battery. It seems to not be an easy diagnosis as I did not find any codes come up. I will say that today the alarm did not trigger while driving, but similar symptoms presented themselves in the morning (no honk during unlock, no flashing blue light for the anti-theft system when locking the car while inside). I was waiting for the blue light to flash and the motion sensor to start while on the freeway, but nothing today. I will see tomorrow in the morning, but also will start the process of getting the car into the shop as this issue is far beyond my expertise to remediate. I will report back if this happens again and will report the ultimate fix.

Edit 1/23 - Welp, it happened again. Similar symptoms at the start of the morning, anti-theft light started blinking after about 10 minutes of driving, short honks of the motion detection started, alarm triggered. Pulled over, turned off car, pressed unlock button on key fob, 2 shorts honk sounded, anti-theft light stopped blinking. No more issues getting to work and no issues while driving home as usual. Bah.

 

When your blue light was flashing,and the alarm started going off,was the alarm just your horn? Or was it a louder siren sound? I have the blue light issue but when alarm starts it's not the horn,it sounds like all the emergency service sirens going off. Just curious.