Alarm goes off for no reason. Message center shows hood is "ajar

factory alarm or after market add on, we can;'t see it
all alarms are just tiny CPU in a box programmed to be and alarm and as such any inputs failing causes and alarm.
doors. ajar switches. even hood,. hatches and trucks.
tampering,
shake switches ( I hate them)<< so do all neighbors.
some have sonic glass breakage sensors.
most cars (for sure this year) the factory alarm can seen as
DTC errors and be seen via the OBD2 port USA./ scan tool.
scan it or get the car serviced..
my car even shows the alarm cause in the CLuster display.

it went off For a reason, that is a fact
most alarms have a way to see logged errors.
if not I defeat the alarm, nobody ever listens to them or even LOOKs. ( everyone is sick of them)<< noise pollution.
good luck
PS read the service manual on the car, chapter ALARM
it has things to do , so read it.

fix door switches

Replace the door ajar switch.

It sounds to me all you need is to adjust the trunk hatch. Its going out when you hit the brakes so the switch isn't bad. It may be worn but if you can push on it and the light goes out it is the reason your alarm is going off. Make sure there isn't debris under the rubber seal preventing it from fully closing.

It can be any of the car door not got properly locked or the door is locked but the switch is not sensing the door locked.Open and close each door again properly.
Or else its problem with any of switch wiring getting in contact with alarm wiring causing it to happen.And last thing alarm connections needs to be inspected.Its getting short somewhere in between.

There are few helplinks with solutions,to troubleshoot these types of problems.I suggest going through these links.
Click the link below:------Volvo car alarm keeps going off for no reason http://technoanswers.blogspot.in/2012/07/volvo-car-alarm-keeps-going-off-for-no.html
------------------ Alarm keeps going OFF http://technoanswers.blogspot.in/2012/07/alarm-keeps-going-off.html
--------------2009 Toyota Camry: Hood Switch causing Alarm to go OFF? http://whatisbyme.blogspot.in/2012/04/2009-toyota-camry-hood-switch-causing.html
----------------Ford Pickup Alarm will not disengage? http://technoanswers.blogspot.com/2012/01/ford-pickup-alarm-will-not-disengage.html
------------Mitsubishi Diamante: Factory Security Alarm will not go Off http://www.howtorepairguide.com/2012/11/mitsubishi-diamante-factory-security.html
------------Toyota Avalon Factory Alarm will go off? http://repairhelpcenter.blogspot.com/2012/01/toyota-avalon-factory-alarm-will-go-off.html
----------Chevrolet Tahoe Hood open warning on dash and alarm sounds? http://schematicsdiagram.blogspot.com/2011/12/chevrolet-tahoe-hood-open-warning-on.html
-----------These details will help.Thanks.

It's in the driver door most likely do you have keyless entry and do you use your key to punch in the #s if so the seal is broken and letting water in if not the driver door module deals with all and also the door wire that's at the latch lock where you close the door that wire could be breaking making the interior and door ajar light comes on but all problems are in the driver door your master lock control keyless entry and alarm and door ajar all go through the driver door module check for moisture in it or corroded connections and broken wires also have fuses checked for blown ones have fun in your techno boogie box and if you do use your key press the key pad buttons get out of the habit

Check the hood pin switch for the alarm, you could of pushed it down a bit when installing the battery so that when the hood is closed it barely opens the switch. Any amount of moisture will make it have contact...also, check the door switch in the door jam. one of them could be bad. if you walk around the car and push on each door individually, you might be able to manipulate it into messing with the alarm or door ajar light. Or just open the door and press it with your finger and see if you find the bad one---I hope this helps.

sounds like the hood alarm switch is not making proper contact with the hood, the alarm will not set properly, check the hood alignment

Not a solution, but details about the same problem with my car: I have a 99 Lincoln Continental and have noticed correlations between certain conditions and the frequency of the car alarm going off.

When it is hotter outside, the alarm goes off more frequently than when it is colder.

The more of a slant the car is parked on, the more often the alarm goes off. My boyfriend's driveway is on an incline and any time I park my car there, the alarm will go off every 30 seconds. If I move the car to the level street, it doesn't go off at all. This has been noticed on other slanted places I've attempted to park as well.

Open drivers door and look at the hinge area. You will see a black rubber accordion looking tube going from the door to the a-pillar. This is the protector for the wiring harness. Wiggle it and see if this recreates your concern. If it does then pop it loose at both ends so you can inspect the wiring.Check each one carefully,feel them and tug on them.You will be looking for one that the wire inside the wiring insulation has broken,the two wires to really look at closley are the YE/BK and BK .
It may also possibly be a door ajar switch sticking and for this take some WD40 and shoot some in each latch on the side of the door and open and close the door several times and this usually un-sticks it.