Z4 alarm keeps going off

[Arbuckle]

Hi guys having some issues with my 07 z4.

My car only gets used every few weeks so I’m aware the battery could be quite low and I’m unsure if this is maybe what is causing my issues.

A few weeks ago my alarm randomly started going off. I was going out every 5 mins and unlocking it with the button and locking it again. 5 mins later same again and again etc. I went out that nights and didn’t leave it unlocked so when I came home at 3am my neighbors we’rent my biggest fans as It had been going off all night. Anyway it seemed to just stop the issue after the next time I took it out and parked it up again.

Today I got a replacement battery and circuit board fitted to my key. I resynced the 2 keys and all was well. Half hour later I went to start the car and it initially tried to start but after 2 seconds it started clicking very loudly. It did this before and I left it a few hours. Went back to it and it worked fine. This time after leaving it an hour I was getting the same issues. I jump started the car and it worked fine so I left it running for 10 minutes then turned it off and locked it.

5 mins later with no one near the car the alarm started going off. I unlocked and relocked and 2mins later same thing alarm going off. Did this about 5 times so Iv just decided to leave it unlocked.

Had a quick read through some threads and found the bonnet switch is usually faulty. Thought must be this and went to unplug it to find no switch there and the wire just taped up to the mounting bracket so it’s definitely not that switch. Locked car and low and behold 30seconds later alarm starts going off. Iv checked doors boot and bonnet are all closed tight.

So back to the original question. Could it be just that the battery is low and causing the alarm to go off ? Any help or suggestions would be appreciated ! Chris

 

[Arbuckle]

Thought I should update I accessed the menu on the car and went to test 19 then test 9 which apparantly shows the battery voltage and it’s showing as 12.1. This is after I had the car running for 20mins

 

[jimbo1958]

Double pressing the lock on the keyfob disables the alarm IIRC.
Won't cure the problem but should give you some respite ubtil you can get it sorted.

 

[Arbuckle]

Didn’t make any difference doing that either :|

 

[Arbuckle]

Went out and stripped the carpets back in the boot hoping to find a tilt sensor maybe submerged in water. The carpets and underneath all seem dry so I don’t think this is the issue.

 

[Arbuckle]

Just trying to keep people updated with what I’m trying.
Tried to press the lock button twice. 30 seconds later alarm goes off. Tried this 4 or 5 times and same thing every time. I thought maybe it’s press lock then hold in lock. The red light on the mirror illuminated for a bit longer as if it was registering the second press but low and behold 30 seconds later alarm went off again. Don’t a lot of reading today about the tilt sensor and I thought it would be in the rear panel in the boot LHS but it’s bone dry in there. Anyone any other suggestions.

 

[MACK]

try the bonnet sensor, its a common fail

 

[Wondermike]

Locking it with the key should keep the alarm off, so you have time to fix the problem.

 

[Ewazix]

Are you sure that you are looking in the right place for the tilt sensor? :?

From what I've read previously the tilt sensor location varies according to model and audio accessories, either in the centre consul between the seats, or combined with the siren located behind one of the rear wheel arch liners. It would be useful to bottom out which is correct for whatever market or model as this problem seems to be cropping up quite a bit.

Tilt only unit in centre consul - Click 'NEXT PAGE' at bootom right to scroll forward https://workshop-manuals.com/bmw/z_series_e85/z4_2.5i_n52_roadst/2_repair_instructions/65__audio_navigation_and_information_system/75__anti-theft_alarm_system/1_ra__overview_of_control_units_modules/

Combined tilt and siren in rear wheel arch http://www.unofficialbmw.com/images/6115EN.pdf

 

[dhobbs]

Disconnect the bonnet sensor. Mine started going off intermittently recently so I replaced it and all fine now.

 

[Ewazix]

Disconnect the bonnet sensor. Mine started going off intermittently recently so I replaced it and all fine now.

His bonnet switch has already been removed..... keep up . :lol:
I suppose this means a previous owner was having the same problem with the alarm, but I would fit a new switch to eliminate possible trips from dodgy taped up wires before looking elsewhere.

Other than the usual bonnet switch, suggestions put forward have been battery first (needs to be min 12.4V after sitting static for a few days), then interior sensors/wiring (has it been fiddled with or tapped in to when fitting aftermarket accessories?), the tilt or tilt/siren unit becoming faulty (depending on which is fitted), the petrol filler flap actuator/sensor being damaged or faulty, or even the GM5 module which regulates and detects locking.

 

[dhobbs]

Disconnect the bonnet sensor. Mine started going off intermittently recently so I replaced it and all fine now.

His bonnet switch has already been removed..... keep up . :lol:

Serves me right for scanning the text
I replaced my rear tilt sensor as the housing was knackered due to the ball joint seizing and putting stress on the unit. Didn't affect my alarm though.

 

[Arbuckle]

Hi guys. Sorry this totally scunnered me so I took a break for a while. Will order up a bonnet switch in case any dampness is playing up with that. I took the left hand side of my boot carpet off and looked about there. Everything was bone dry and there wasn’t any signs of damp so I’m guessing the tilt sensor is in the front somewhere.

On a side note. My car suffers really badly from condensation inside the windows in the winter so there could be an issue with damp somewhere so that would tie in with the tilt sensor maybe throwing faulty readings.

For now Iv been opening with keyfob and locking via key to stop the alarm going off but keen to get to the bottom of it so if anyone has advice on getting to the tilt sensor inside I’m all ears.

 

[DMike]

Double pressing the keyfob locks and arms the alarm without the interior motion and tilt sensors, for parking with pets inside or aboard ferries, trains and similar. So in your case it could be any of the other sensors (doors, boot lock or bonnet). I’d suggest charging the battery completely and then reading sensor statuses using INPA or similar.

 

[Arbuckle]

What is INPA. ? Something I can do myself or need to take it to garage ?

 

[Ewazix]

...........................I’m guessing the tilt sensor is in the front somewhere.
......................... so if anyone has advice on getting to the tilt sensor inside I’m all ears.

Scroll up three places to my first post, click the first link to a web page and second link to open the PDF they cover all versions of switches, tilt sensors and siren. :lol: /

 

[Arbuckle]

I’m struggling to follow mate off the diagrams. What do I need to remove. I don’t know what it means with rear storage box. How difficult is it to remove the tilt tensor and if you unplug it would it set alarm off or stop this from happening.

 

[Ewazix]

I’m struggling to follow mate off the diagrams. What do I need to remove. I don’t know what it means with rear storage box. How difficult is it to remove the tilt tensor and if you unplug it would it set alarm off or stop this from happening.

I've had my centre consul partially removed to get at the CD changer and you are right, it's tricky! So don't go stripping the centre consul until it's established whether your model has the tilt located in the centre consul, or combined with the siren which is located in the RH wheel arch.

I think it depends on the year, model and whether it's a UK/Euro or US market car, to check what is fitted to your car have a look at RealOEM, it's best to search via the last 7 digits of your VIN number. If not click through the year model etc making sure you select Euro or US and LHD or RHD as appropriate. Once you get to the main page the alarm parts you are looking for will be under 'Audio navigation electronic systems'.
To further complicate matters BMW have fitted several versions of the part, so Real OEM list the various part numbers and the latest version which is the one you might end up ordering from BMW...... this will determine whether it's a tilt in the centre consul or wheel arch.

https://www.realoem.com/bmw/enUS/select

The other way is to have look at the one in the wheel arch and see if the combined tilt and siren part or just the siren, it's much easier to get at.

Or if you really don't know what you are doing keep the sensors switched off for now until a tech can check it.

 

[DMike]

What is INPA. ? Something I can do myself or need to take it to garage ?

INPA is BMW diagnostics software that via OBD-port reads error codes, sensor statuses and lots more. Available from garage, forum members or ebay bundled with OBD cables.

From what you have written the tilt sensor is not the culprit: When locking by pressing twice (with clown nose lighting for a second indicating you did it correctly) your alarm is not responding to tilt sensor or motion sensor status - and the alarm still went off. The bonnet switch is by far the most common fault and if you are 100% certain (metered or replaced) that it’s ok, obd diagnostics is the way to go saving time and trouble.

 

[DMike]

Took a look at the wiring diagrams. Boot and bonnet sensors are just simple closed circuits connecting to GM5 so there’s probably not much to see with INPA.