Rapid High-Pitched Beeping?

This is maddening and I wonder if anyone has a clue: Since I bought my 2002 C4 Cab 4 months ago, roughly every 2-5 trips while driving the car it will emit a loud, rapid high-pitched beeping for about 5 seconds straight, followed by about 30 seconds of silence, followed by 2 chirps. The sound seems to be coming from somewhere in the dash. There seems to be no rhyme or reason as to when during the trip the beeping occurs (although never at the very beginning or end of the trip). I have a Valentine One installed, but I am familiar with the beeps from that and I don't think it's related (not to mention these beeps happen even the the Valentine One is turned off). Anyone have any ideas? Thanks!

Brad, have you checked for any other add-on electronics? Such as a LoJack system or Laser Jammer or... any electronics hooked to the radio. etc. etc.???

No and you make a good point; POs had made several mods to this car (intake, exhaust, Valentine 1, short-shift etc..) and documentation is limited, so it may be possible that it could have other add-ons which could be the source. I'm going to hunt around under the dash, frunk etc.. right now and will see if I find anything.

yea, I'd start under the dash and look for any unusual electronics feeding 12V off the fuse box. Sometimes people would mount trackers under the dash and they'd beep if the backup battery was going dead. Just a thought. Hope you find the problem... that can be very annoying.

Well Ive looked and am not seeing anything weird, but I am new to these cars and I could be missing something. Only thing in the trunk is the amp for the stereo. Any of this stuff look suspicious?

Looks pretty stock to me Brad... keep noising around. Are you able to locate the noise when it's beeping?

Thanks for your help..source of noise seems to be front left (inside car), but hard to pinpoint. Local shop couldn't reproduce it so I guess I will have to do go full MacGuyver myself. Harder since it only happens while driving.

Look in the front bumper grill and rear license plate frame. You may find what looks like a small red or black box. That would indicate that you have a laser jammer installed somewhere.

Well, I'm not claiming to be an expert on this problem, but if you can't located any add-on electronics, the problem may be related to the Alarm/locking system. And that's a hard one to diagnose properly. I've seen some rare situations where people would get random series of beeps while driving. Does your car beep when you lock and arm the car? Okay, so here's the deal, your immobilizer module is located under the seat and has a backup battery system inside. When that battery starts to malfunction, you'll get random beeps. That may be the culprit!

Also, this is something I had to turn off... but do you have the speed limit indicator on? If so, what speed? For example, if you set it for 60 mph, when you hit that speed, if will give you warning beeps and a graphic on your gauge display.

B3Freak, I will check the immobilizer module and speed limit indicator battery, thanks. Wyovino, nothing around the rear license plate (pried around, let me know if I actually need to remove it). Only 2 items of interest in the front bumper are below; I assume one or both of these are related to the Valentine One?

^^That first picture is the OEM air temp sensor. The second pic... I don't know... hard to tell. btw brad... you need to vacuum your vents! (notice leaves) haha

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What's that weird looking stuff back by your radiator?

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RennRoach did it, you should know that! haha!

Yeah noticed that..just debris which Ive heard is common..cleaning that s**t out today, thanks for getting me to look in there!

B3freak, to answer your other question, no the car does not make a sound when I lock and unlock using the key remote (as I prefer it).

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That little biotch!

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Ok, my guess is the immobilizer's back up battery may be going bad which alerts with random series of beeps. Not a 100% on this. But if somehow you could pinpoint it next time. Noooo.... I'm not suggesting you dip your head under the seat the next time you're driving. Maybe have your significant other could do it? Might enjoy it if you get my drift. hahahaha

I'll explain to her that its all in the name of science.

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When I hear that sound, it's typically my mother-in-law backing up. Ba-dum. Psh.

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Well I'm no expert either but I've been part of the 997/996 community for 10+ years and I've never heard of a backup battery associated with the immobilizer. I thought the immobilizer was like all other cars in that it is a passive transponder chip in the key recognized by the ignition switch during the starting sequence. Can you provide some more info? Thanks.

^ +1 I was not aware that the immobilizer has a backup battery, and I've never seen anyone DIYing (or otherwise) this backup battery. I _believe_ that RoW 996 alarms have a separate siren with a battery backup in the front trunk; I don't think North American 996's are so equipped. To the best of my knowledge, the central locking system's "beeps" are the horn sounding, not a speaker or piezo buzzer in the cabin.

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I do have to agree. Never run across this one. Has to be something else.

Well I'm confused as hell, especially now that the immobilizer and alarm seem to have been ruled out. The sound isn't anything more than an annoyance, but it means something and I'd like to find out what. I will keep digging around and will try to pay close attention to the location when it goes off again. I will keep you posted, whether you like it or not.

I recently rented a 2002 Boxster. Driving down the highway I hear a series of chirps. Someone had set the "maximum speed indicator" to 65. If I went over it, it chirped at me. More of a scolding really. I just turned it off and all was quiet. It is hidden in the submenu where you check oil levels, reset milage, etc. Not sure if your 996 has the same feature. They do share lots of the same innards.... I'll have to look at my 2001 996TT when I get home.

KC-CarGuy, thanks I forgot that someone already mentioned this. I found the submenu; the limit was set at 30mph, but the box to the left of "limit activated" seemed to be unchecked. Just to be sure, I changed the limit to 180mph, but Im guessing this is not the issue.

If it's not the speed limit switch, I'd guess, as have others, that the previous owner added something aftermarket and you just haven't been able to find it yet. I bought a used 997 turbo 5 years ago and found a K40 remote in the center console but all the parts related to the K40 had been removed...except for a Bluetooth module in the rear driver's side tail light. I discovered it when I was trying to pair my wife's iPhone to her car and I kept seeing this odd Bluetooth device showing up. Any chance you can contact previous owner? Good luck.

jhbrennan, I have a hunch you're right. I've contacted a couple of the previous owners, unfortunately it seems to be the first owner who did all the mods, but he changes cars often and since it's now been 13 or 14 years since he owned the car, he doesn't remember exactly what he did. I think I'll keep sniffing around, and try to pay close attention to the origin of the sound when it happens.

This is fascinating. I thought for sure the speed monitor was the culprit.

Well perhaps I am misunderstanding the speed monitor settings. Here are 2 shots I just took; in my mind the first photo shows a DEACTIVATED speed alarm, and the second shot (with the black block within the square) shows an ACTIVATED speed alarm. Do you guys agree?

Yes, I believe you are correct that the box when ticked is active and when un-ticked is inactive. I suspect setting it to 180 should limit how often you set it off (unless I'm underestimating your need for speed)... I find the urge to wet myself at any speeds above 150 is adequate to remind me to slow down; an additional electronic reminder is not necessary.

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To really clean it you need to pull the bumper cover and separate the air con radiators from the engine rads. Porsche 996 986 bumper removal - YouTube Cleaning a Porsche 996's radiators - YouTube

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That is not a part of a stock valentine one. I guess its part of a laser jammer.

Interesting, here are 2 more photos of the "black box". A cord (power I assume) comes out of the back as you see, and threads into the bumper. I haven't followed it further. No name or number on it, which could make sense if it was a laser jammer or something similar. Look familiar to any of you?

OK we may be getting somewhere, have a look at this: http://www.antilaser.ca/images/alg9_sensors.png

Doesn't look like a K-40, but a laser jammer none the less. I win. How many internets do I get?

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Yea, I could be wrong or the pusher of bad information because I dug it up from past discussions on RL.

Wyovino yeah props for id'ing the laser jammer. You win the same thing I win when I beat someone on words with friends: roughly 8 seconds of satisfaction.

Fpb111, thanks for the links to those videos on properly removing debris from the radiators, I will check them out

On a positive note (pun intended) you have switched power available to you in the bumper and frunk should you need it for a project. I tapped into mine for daytime running lights.