Measuring Honking through OBD

Question

This is probably too simple question for this forum but would appreciate your help anyways. I was wondering if I buy and connect a OBD port to my car and is successful in collecting data, would there be any data which would tell me directly or indirectly how much I have honked during the day or during a particular drive? In other words, is there any data collected by OBD2 port at all which measures the level of honking?

Answer 1

On a fancier car with a very customizable body control unit, you might be able to see when the horn button is down with a CANBus interface, but probably not even then. OBDII doesn't deal with car accessories and is just there to expose engine related data.

Horns are too simple and are a required safety device that is not customizable so I would think they have their own circuits and are not tied in to any computer system.

Answer 2

It depends what make and model of vehicle.

PSA after 2003, VAG after around 2005-7, BMW depends but all after 2008 have the horn controlled by the BCM (or whatever they each choose to call it). Many other makes may also have the horn controlled by the BCM.

So it is possible to see if the horn is actively being pressed through the CAN bus if the horn is controlled through some sort of BCM, it may or may not be available on raw data bus and most definitely will not be available through standard PIDs as these deal with engine and safety systems.

You will have to monitor the CAN bus data and keep pressing the horn (you could disconnect it to not annoy the neighbours!) if you see some data change you then watch it more closely to be sure that this data bit is in fact the horn. If the horn status is not on the raw data things get more tricky but it still may be possible, you would need to access a good diagnostic scanner which can communicate with the BCM and give live data. View the live data with the scanner at the same time as monitoring the raw data, you will notice more IDs appear, these are reserved for communications with diagnostic tools, you can now monitor these as above for changes when the horn is pressed.

The BCM doesn't do any data logging so you will have to do this yourself which is simple enough if you have basic to good electronic and software skills or there is data loggers available to buy but getting them to work with manufacture specific PID / codes can be hard to impossible. You would need this plugged into the OBD port or connected anywhere else to the CAN bus for the entire time you wanted to log horn presses.

As you can tell it may be a rather complicated task but certainly doable if the horn is controlled through a control module and that control module is connected to a CAN bus.