FAQ - Alarm Siren & Alarm System Trouble Shooting

SwissJetPilot · Jun 13, 2018

These post covers several different topics -

1. Alarm Fault Codes
2. Alarm Siren Replacement
3. NiMH Battery Replacement
4. Shutting off the Alarm with VCDS
5. Switches on the Edge of the Driver's Door
6. Testing The Alarm -
7. Setting "Chirp" Confirmation On or Off

There are a set of Ni-MH battery inside the alarm housing with a lifespan of about 6-8 years. When these batteries fail, they tend to corrode which can severely damage the PCB. The resulting damage can lead to other problems and fault codes associated with, but not limited to, the Comfort System Central Control Module -J393- since the signal to/from the -H12- can't get to the CSCCM.

According to the 7Zap parts website, the Mk2 TT Alarm Siren is part number 1K0 951 605 C for all production years (2007-2014). However, there's no point buying a used revision C as the NiMH batteries inside will be at least as old and defective as the ones in your own alarm siren. If you want to buy a used one from eBay or other reseller, be sure to check the revision and date code so the batteries are as new as possible. You can read about decoding Bosch date codes here.

Update - As of February 2022, Audi's parts department quoted me € 201.91 (not including VAT) for a brand new 1K0 951 605 F alarm siren.

1. Alarm Fault Codes

• 01134 - Alarm Horn (H12): No Signal/Communication
• 00470 - Combination comfort Databus in Single Wire: Open Circuit
• 16346 - Control Module Faulty static

Possible Symptoms
• Anti-Theft Alarm sporadically triggered
• Inability to change the Lock/Unlock Acoustic Confirmation (chirp) with VCDS or OBDeleven

Possible Causes
• Fuse(s) faulty
• Failed batteries or damaged PCB inside the alarm case

Possible Solutions
• Check Fuse(s)
• Check Wiring and/or Connector(s) from/to Alarm Horn (H12)
• Check/Replace Alarm Horn (H12)

Changing the alarm 'chirp' with VCDS -
https://www.ttforum.co.uk/forum/viewtop ... &t=1380409

Solving the 01134 alarm fault codes -
https://www.ttforum.co.uk/forum/viewtop ... &t=1834061

2. Alarm Siren Replacement

Here's a nice DIY by HappyChappy which includes step by step photos.

How to Replace a Faulty Alarm Siren
https://www.ttforum.co.uk/forum/viewtop ... &t=1982823

Basic removal & replacement procedure -

• Remove driver's side wheel (right fender/wing)

• Remove arch liner

• Remove plastic bung on top of wing under the bonnet

• Undo 13-mm bolt (use a proper penetrant spray, not WD-40 if the bolt won't come loose)

• Slide horn cradle out

• Unplug old siren

• Replace with new siren

• Reverse order of dismantle

Thanks to Legend_of_Chaos for the instructions!

View attachment 434559

3. NiMH Battery Replacement -

For anyone who wants to attempt a repair, if your PCB board is still in good shape look like the one shown below, it may be cheaper to just replace the batteries. As you can see, there is little if any damage as the batteries have not leaked. So if you're handy with a soldering iron, this may be another option to spending 90-Euro on a replacement siren.

How To Replace Batteries in the Alarm Siren
https://www.ttforum.co.uk/forum/viewtop ... 1#p9354981

Thanks to John949 for the instructions!

Battery Source -

Battery Varta 2x3/V150H 7.2V 140mAh NiMH Rechargeable Pack 8 Pin

If you can't find a single 7.2V 2-pack, you can use two of the Varta Mempac 3.2V/150mAh batteries described in John949's Battery Replacement DIY.

Varta NiHM Battery Information and Data Sheet downloadable PDF files -

As noted in this diagram, if the H12 Alarm Horn signal isn't getting out because the PCB is damaged, it can result in triggering one or more DTCs and prevent changing the "chirp" settings with VCDS or OBDeleven.

SwissJetPilot · Sep 26, 2022

4. Shutting off the Alarm with VCDS -

In the event your alarm is going off at all hours of the night and you know it's because of a defective internal battery, you can deactivate the alarm system it with VCDS. The doors will still lock as normal, and turn signal blink when lock/unlocking. But be sure to replace the siren as soon as possible and don't forget to reactivate the anti-theft system once you have the new siren installed.

Address 46-Central Convenience > Coding > Long Coding Helper > Byte12 - Check Bit 0 Anti Theft System Deactivate

And for anyone who's interested, here's what a Thatcham alarm is all about -

Thatcham devices: what is Thatcham Category alarm | RAC Drive

Find out what thatcham category car alarms are inlcuding Thatcham Category 1 and 2 alarms and how they work for car security systems.

www.rac.co.uk

SwissJetPilot · Aug 25, 2025

Additional pictures with the fender removed just so you can what you're dealing with -

SwissJetPilot · Aug 27, 2025

5. Switches on the Edge of the Driver's Door -

Interior monitoring

Interior monitoring registers movements inside the vehicle and then triggers the alarm.

Fig. 44 Interior monitoring button in the door trim (only visible when the driver's door is open)

You should switch off the interior monitoring if there is a possibility that animals or moving objects in the vehicle interior could trigger the alarm. The tow-away protection monitoring should be switched off if the vehicle is to be transported, e.g., by rail or ship, or towed.

Deactivate interior monitoring

Press button (A) and turn page 54, Fig. 44
Lock the vehicle

Deactivate tow-away protection monitoring

Press button (B) on the door
Lock the vehicle

If the interior monitoring or tow-away protection monitoring is activated, the LED in the button lights up and the LED in the instrument panel also lights up for approximately 3 seconds. After locking the vehicle, the LED in the instrument panel flashes rapidly for about 3 seconds. About 30 seconds later, the LED begins to flash slowly. The interior monitoring or tow-away protection monitoring is automatically reactivated the next time the vehicle is locked.

ATTENTION!

When the vehicle is locked from the outside and the anti-theft alarm is activated, no persons—especially children—may remain in the vehicle, as the doors and windows cannot be opened from the inside. Locked doors make it difficult for emergency responders to get inside the vehicle—this is life-threatening!

SwissJetPilot · Aug 27, 2025

6. Testing The Alarm -

If you want to ensure the alarm works as it should you can do it by -

• Opening the windows with the key fob (hold down the unlock button)

• Set the alarm with the key fob (lights should flash twice, or the siren will chirp)

• Wait about 60-90 seconds for the system to set

• Reach inside the vehicle and wave a shirt, jacket or towel.

That should set off the alarm.

7. Setting "Chirp" Confirmation On or Off -

When the alarm is set, it will either chirp (confirming the alarm works) or the lights will flash twice. You can change this setting with VCDS, OBDeleven or most OBDII diagnostic devices. Look under Address 46 - Central Convenience or Comfort System. Find Hex 05 and select/unselect one of the two options shown below. You can turn either one on and one off, or both on or both off.

FAQ - Alarm Siren & Alarm System Trouble Shooting

Attachments

Thatcham devices: what is Thatcham Category alarm | RAC Drive

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