Alarm going off - 2006 E86

[Fred Smith]

Yesterday I got the remote to work, so for the first time since purchase I can lock and unlock the car without using the key!

Hurrah!

Today the car alarm has gone off three times for no reason (that I can see). The alarm has not, to my knowledge, gone off once in the last 3 or 4 months.

Help!

 

[j3nks79]

Give it a scan to see if you have any errors with the sensors etc.
when you use the key to lock it doesn’t arm the alarm btw

 

[Fred Smith]

Next time it goes off I will lock with the key. Thanks for giving me a solution that turns this issue for "fairly urgent" to "can be dealt with next year or the year after if necessary!"

Tonight I will see if I can find the bit of paper with the two error codes that Zedebee kindly identified on my car, and see if they might be relevant. I might also read the manual as it relates to security (I hate reading manuals).

As an aside I am currently in a position whereby I own two cars and literally the only key I have for either of them that works fully is causing me a bloomin' alarm issue! My other car (what should be my daily really, but is currently SORN having been lent and stopped working!) has two keys, neither of which are capable of starting the car let alone anything else fancy like remote locking!

 

[Lynchy]

Disconnect the bonnet sensor as this can cause the alarm to go off. It won’t effect your alarm if you do this

 

[buzyg]

Disconnect the bonnet sensor as this can cause the alarm to go off. It won’t effect your alarm if you do this

This worked for me too. Worth a try dead easy to do.

 

[Fred Smith]

Disconnect the bonnet sensor as this can cause the alarm to go off. It won’t effect your alarm if you do this

I will give that a go... curious to see if it goes off again... when it does I will look at that first

 

[Zedebee]

The bonnet sensor is the small cubic device where the diagonal braces meet.

 

[Fred Smith]

The bonnet sensor is the small cubic device where the diagonal braces meet.

Yeah, I googled it and found it... the car doesn't like it being disconnected, I think the next step is to disconnect it and jump the input connector to trick the car into thinking the sensor is on and the bonnet is closed.

 

[Mike6]

Try disconnecting the battery and leaving it for 30 minutes. Often works for a multitude of issues. If battery is old a new one might help.

 

[brillomaster]

The bonnet sensor is the small cubic device where the diagonal braces meet.

Yeah, I googled it and found it... the car doesn't like it being disconnected, I think the next step is to disconnect it and jump the input connector to trick the car into thinking the sensor is on and the bonnet is closed.

were you disconnecting the sensor while the ignition is on? i've disconnected a few faulty sensors in my time (indeed, it used to be the first thing i did to a new cheap track car) and have never had a problem doing so. i've also yanked out interior motion sensors before as well, again with no ill effects.

 

[Fred Smith]

Try disconnecting the battery and leaving it for 30 minutes. Often works for a multitude of issues. If battery is old a new one might help.

Doesn't disconnecting the battery also often cause multiple issues?

 

[Fred Smith]

were you disconnecting the sensor while the ignition is on? i've disconnected a few faulty sensors in my time (indeed, it used to be the first thing i did to a new cheap track car) and have never had a problem doing so. i've also yanked out interior motion sensors before as well, again with no ill effects.

No, the ignition was off. Disconnecting the sensor seemed to trick the car into thinking the bonnet was open, and therefore wouldn't let the remote locking work.

 

[j3nks79]

were you disconnecting the sensor while the ignition is on? i've disconnected a few faulty sensors in my time (indeed, it used to be the first thing i did to a new cheap track car) and have never had a problem doing so. i've also yanked out interior motion sensors before as well, again with no ill effects.

No, the ignition was off. Disconnecting the sensor seemed to trick the car into thinking the bonnet was open, and therefore wouldn't let the remote locking work.

Must be working then

 

[Fred Smith]

Must be working then

Not sure that logic works. I think that the sensor might be intermitant - it works enough to know the bonnet is shut and it can allow the remote to work, but doesn't work consistently enough. As a result the car suddenly detects something and sets off the alarm.

Maybe I am wrong.

If I disconnect the sensor, then connect the input and output of the input clip for the sensor, then this should tell the car that the sensor is giving a 100% solid "bonnet shut" reading, and if this sensor has been playing up and causing the alarm to sound then jumping the ins and outs will stop the alarm going off and prove that the sensor was the issue. I think!?!?!

 

[j3nks79]

Must be working then

Not sure that logic works. I think that the sensor might be intermitant - it works enough to know the bonnet is shut and it can allow the remote to work, but doesn't work consistently enough. As a result the car suddenly detects something and sets off the alarm.

Maybe I am wrong.

If I disconnect the sensor, then connect the input and output of the input clip for the sensor, then this should tell the car that the sensor is giving a 100% solid "bonnet shut" reading, and if this sensor has been playing up and causing the alarm to sound then jumping the ins and outs will stop the alarm going off and prove that the sensor was the issue. I think!?!?!

But you don’t know if that sensor is actually the issue.
You could be into a red hearing.

You unplugged it and it wouldn’t let you lock the car.
You plug it in and the remote locking works.

If you don’t have a code reader or INPA etc to check you are just chasing your tale.

 

[Zedebee]

Try disconnecting the battery and leaving it for 30 minutes. Often works for a multitude of issues. If battery is old a new one might help.

Doesn't disconnecting the battery also often cause multiple issues?

I’ve never had an issue disconnecting the battery (and I disconnect it every time I need to unplug a connector or sensor), however a low/undervoltage battery is known to cause issues.

 

[Fred Smith]

But you don’t know if that sensor is actually the issue.
You could be into a red hearing.

You unplugged it and it wouldn’t let you lock the car.
You plug it in and the remote locking works.

If you don’t have a code reader or INPA etc to check you are just chasing your tale.

Fair... but that sensor seems to be a common issue. Will dig out the codes I have. Will consider a code reader (ideas for BMW / Z4 specific and more general, app with adaptor or all in one)

Edit - no! If the sensor is bypassed and I use the remote and the alarm doesn't go off, then it is the sensor causing the issue. I have not checked the remote without the sensor, and if I do that and the problem goes then it's probably the sensor.

 

[j3nks79]

But you don’t know if that sensor is actually the issue.
You could be into a red hearing.

You unplugged it and it wouldn’t let you lock the car.
You plug it in and the remote locking works.

If you don’t have a code reader or INPA etc to check you are just chasing your tale.

Fair... but that sensor seems to be a common issue. Will dig out the codes I have. Will consider a code reader (ideas for BMW / Z4 specific and more general, app with adaptor or all in one)

Edit - no! If the sensor is bypassed and I use the remote and the alarm doesn't go off, then it is the sensor causing the issue. I have not checked the remote without the sensor, and if I do that and the problem goes then it's probably the sensor.

I may have misread but I thought you said it wouldn’t remote lock with sensor unplugged?

 

[Fred Smith]

I may have misread but I thought you said it wouldn’t remote lock with sensor unplugged?

[If I understood the guy at the auto key place I was at today, and if he was right]

Edit - I think this post is nonsense!!!!

With the sensor unplugged the CPU thinks the bonnet's open, because the sensor isn't closing the circuit. Therefore the remote doesn't work and the alarm isn't set so it can't go off for no reason.

If the sensor is faulty it risks telling the CPU that the bonnet's open when its shut (edit - and this sets the alarm off if the alarm has been set by the remote). If you simply disconnect the sensor the circuit remains open and the CPU thinks the bonnet's open, so you can't use the remote and the alarm doesn't get set. So if you disconnect the sensor you need to jump the input connection to the sensor to replicate what the sensor should do when the bonnet's shut.

If the remote works with the input and output to the sensor jumped, then the remote locking of the car will set the alarm, and if the alarm doesn't go off then I know it was the sensor setting off the alarm.

At least I hope I understand correctly.

 

[enuff_zed]

Everyone else unplugs the sensor and tucks the wire back out of the way. Never heard of that not working before. I’ve done several myself and bought cars that have had it done. Pull the plug off and carry on using the key fob to lock unlock and activate the alarm.
Seems you have a unique problem?