Your BMW may not start in cold weather. This can affect all BMW vehicles including 1, 3, 5, 7, X1, X3, and X5 series.
BMW Hood Switch | Bonnet Sensor Replacement Guide
In this guide, you will find instructions on how to replace the BMW hood switch, also known as the bonnet alarm sensor or hood sensor.
A common problem with the BMW hood sensor is that you get a hood open message on the dashboard even when the hood is closed, or the car alarm goes off at random times without anyone touching the car. In the majority of cases, this problem is solved by replacing the BMW hood switch.
A bad hood latch switch can cause a warning message on the dashboard / iDrive or trigger false alarms. The sensor may fail on its own.
- Hood warning message on the dashboard
- The car alarm goes off randomly when the car is locked.
- False bonnet open warnings on iDrive
The most common signs of a bad BMW hood switch are hood open (bonnet open) warning and false alarms.
Often a BMW owner may notice these symptoms after a car wash.
To permanently fix this problem, you will need to replace your BMW hood switch. The procedure is very simple and takes about 15 minutes.
- Park your BMW, set the parking brakes, turn off the engine.
- Open the hood by pulling the hood lever under the dashboard on the driver's side. Pull or press the hood release at the front of the hood and lift up the hood.
- Locate the hood switch towards the back of the engine. The hood switch is on top of the plastic that's over the firewall.
- Press the connector and unplug the wire harness from the sensor.
- Remove the sensor from the bracket using a flat head screwdriver. On some models, you may need to remove the cabin air filter housing to remove the hood switch.
- Install the new sensor by pressing it in the bracket.
- Connect the wire harness to the hood switch.
There are a few temporary solutions that you may want to consider until you get a BMW hood switch replaced. Note that these solutions are not recommended for the long term.
The recommended fix is to replace the BMW hood sensor with the new one. The sensor is inexpensive and ranges in price from $10-$30.
- Disable Hood Switch: When you lock the car using your key fob, press the BMW logo on your key twice. This will disable the input to the alarm system from sensors such as the hood switch. Note that doing so means that it may be easier to break into your BMW.
- Disconnect Hood Switch: Unplugging the hood sensor is another temporary solution. Note that by unplugging the wire from the sensor, you are disabling input to and from the sensor.
- Repair BMW Hood Switch: Remove the switch and open the housing. Clean the contacts inside and manually stretch (lengthen) the spring inside the sensor. This will usually fix a BMW hood open problem, but the problem may return within a few weeks or months.
- Can I test the BMW hood switch?
- Yes. You can test the switch by using a digital multimeter and measure continuity. The sensor has two settings. Open circuit and closed circuit.
- I replaced my BMW hood sensor but still have problems.
- Check the wiring to the hood sensor. Also, check the age of your car battery and the micro-switches integrated into the hood latches at the front of the hood.
Published on: Wednesday, September 19, 2018.