jpohl402

Hello gentleman,
Was wondering if anyone had any experience with this particular issue and could possibly point me in the right direction (as to where to begin troubleshooting.)

To preface this: I have already been to two mechanic friends. They each took a BRIEF look at the vehicle after I described the problem. Both times a scanner was hooked up, codes were read (nothing about the issue!!), then all was CLEARED. We tested the issue and were able to duplicate it in one of the instances.... But they had no clue where else to begin looking within diving into some electrical wiring diagrams, slowly troubleshooting, and reading the internet mechanics database for documented problems (now I don't remember the name... maybe AllData.) Anyway, what they did so far was FREE but I would have to pay (of course) if I wanted the issue properly diagnosed and (hopefully then) repaired. No surprise there, that's fine... But maybe somebody here has been through this, and it's potentially an easy fix?!

So here is what the car does: My daily driver/winter/bad weather car, a 2007 Impala.
Issue began a few months ago. I always always used the remote keyfob to lock the vehicle upon exiting. Then in the middle of the night I heard the alarm going off. Went outside expecting to maybe see a broken window. Nothing of the sort. Unlocked, opened door, locked car again. A fluke. Back to bed I went. Then a few hrs later - same thing - the damn alarm going off again!! Strange... Still nothing was amiss. The next morning when I actually started the car, the gauge cluster read "theft attempted" or something similar right away!
I disregarded. Literally almost every time since then that I locked the doors with remote, AT SOME POINT, the alarm would go off! Sometimes the car would be parked for 3-4-6 hours before it happened, but it would! OR, sometimes the alarm would literally begin going off after THREE minutes! I couldn't even make a quick trip inside a store, come out and the alarm is sounding by then. Now, as you know, the lights flash which causes a drain on the battery. But more importantly, the loud annoying horn honks!!

Most times, I would say the alarm begins to sound after between 10 and 60 minutes after being activated. Now I often make short trips and make a lot of stops in the day. So after 4-5 days of this I was fed up!
I went to see my first mechanic friend. To further elaborate on the above visits: at his request, we tried to lock the doors/car from the INSIDE, using switch on driver door panel then closing driver door. Alarm engaged, car locked, great - hopefully it won't sound! I can use the door switch as opposed to remote, whatever... But Literally two minutes later, it starts going off!

Soooo then I discuss with him the best two scenarios in MY EYES:
1. We completely disable the alarm system altogether. Doors will lock, no anti-theft system. Big deal. If someone wants to steal this cheap beater car by breaking in, oh well! At least I can lock my doors and I was willing to take that chance. After doing some research however, he told me that you cannot disable the anti-theft system because it is tied in to the rest of the modules/etc. So a no go there! He would have done that for free even.
2. Remove the fuse for the horn! The lights will flash but at least the horn won't honk... He advised against this because even if the car isn't honking the flashing lights draw attention and also cause drain to battery.
So on that day, I REMOVED the keyfob remote from keychain and have a single key only - that way I am not tempted to lock the car with remote by force of habit!! And I've just been leaving the car unlocked! For maybe two months or so now...

During this time I consulted with the other mechanic briefly and he had no ideas for me, seems like a strange problem I guess....

I will point out ALL other wiring & electronics are fine and without issue. There is NO aftermarket radio, no amp, no subs, no Nav or GPS unit plugged in, etc. Everything else functions without problems....

Now I don't live in a high crime area or leave anything valuable in the car, not too concerned about it, whatever - but would be great to have the ability to lock her again!!
Thanks in advance for any help or advice!

sledge.impy

This is the factory alarm? You didn't quite say.


The older cars must be different for some reason.. locking doors doesn't set the alarm.

Even my 2002 j-body had a separate lock/alarm modes.

How old is the battery?

jpohl402

Thanks for your reply!
Factory alarm, yes, sorry.
On this model ANY locking of the doors while car is off seems to engage the anti-theft system.

Battery, without looking at the stamped date but off the top of my head, approx 1.5 years. No more than 2 years old. Sometime in 2013. So well within it's lifespan...

Frank3

Didn't the earlier Impalas such as yours have an "occupant sensor" in the trunk that was intended to prevent kids from being injured by high temp exposure by being trapped in the trunk? I don't remember if it worked by movement or temperature, so this could be a possibility. Also you mentioned I think the battery was about 1.5 years old, that is good but how are the cables, any corrosion? Lastly, I had a problem with my 2001 Impala and the alarm, but it was throwing codes and lighting if I remember correctly a check vehicle light. The BCM was having issues when the lights and the horn were triggered by setting the alarm. A new BCM solved the problem. My sister in law had a problem with her Olds Aurora factory alarm causing the lights and horn to flash and sound while going down the interstate. That was a BCM problem as well.

jpohl402

Frank, Thanks so much for those tips! I will explore those possibilities if needed. Yes, I believe it's all connected thru the BCM unit, and that is potentially the cause of my problems.
As far as battery connections & cables go - they are pretty clean, connected tightly, and free of corrosion! Interesting about your sister in law's issue as well.

I also have a new avenue to explore, based on a tip from a local dealership after a phone call today. After describing the problem, and having no codes to trace (requiring tracing wires and hourly diagnostic fees if I were to bring the car in) - he thought I may have a faulty remote control fob. If the circuit shorts out (at whatever time), it would cause an interruption in the transmission of codes, and trigger a fault thinking someone was attempting to steal the car! Short of buying a new remote with programming costs, and I only have one currently, he suggested I lock doors with keyfob, then immediately REMOVE the battery. The car remains locked with alarm engaged. As long as the remote isn't sending faulty codes to car, the alarm should NOT go off! Now, I cannot use the actual key to open the door because that would trigger the alarm there. I need to put the battery BACK IN, then unlock with remote. However, if the alarm doesn't go off AT ALL for 3 or 4 days, the problem likely lies with a faulty transmitting remote!! SO FAR (it's been about 3 hours parked/locked) - NO alarm...

I will keep this forum updated for the greater good of the community, and future reference! Thanks

sledge.impy

Maybe you need a new remote battery too? 2003 is getting pretty old...?