Wondering how I would be able to send signals to my car (ford focus 2014) in order to turn on and control lights on the dash and various alarms in the car such as the open door alarm and car alarm.

We have been using an Arduino Uno with a CAN-BUS shield to access diagnostics and receive signals (such as RPM/Speed) from the OBD port but are having difficulty figuring out how to send signals to the car to programmatically turn on/off functions of the car.

There is little documentation out there, but people have said that it is possible. My question is how do you go about coding the Arduino to send signals to the car.


  • There are two parts to this question. The first is, painstakingly reverse engineer the CAN bus to find the messages that you need. The second is, follow the Arduino CAN tutorials. There is little documentation because the manufacturers don't release it. If the second question is more important than this should be migrated to the Arduino forum. – vini_i Oct 9 '19 at 19:00
  • The things you listed (door ajar, alarm) sound more like they come from the BCM or as ford likes to call it sometimes the SJB. Usually they are simple Hi/Lo signals to the SJB that then sends a can message to the cluster. Is it out of the question to just send the signals at the SJB and let him tell the cluster? – narkeleptk Oct 9 '19 at 21:11
  • Thanks! I'll have to do some research into that to see if that may work @narkeleptk – Carol Oct 9 '19 at 23:10
  • @vini_i thank you! Ya it's been a pain trying to reverse engineer the can messages, we can't seem to pin point the right ID for some of the actions we want to perform. I may take your advice and migrate this question to the Arduino forum and try to do more research. Thanks again – Carol Oct 9 '19 at 23:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.