Sign up ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.

I am investigating the possibility of monitoring and controlling the car cabin temperature using GPRS. I will be using Arduino Uno and GSM shield to communicate with an Android App. The arduino works as a bridge between the mobile app and the car. I initially thought i can achieve this by connecting arduino to the OBD-II through ELM327 but apparently it is not possible. Do I need to do some physical wiring to be able to start the car and switch on/off the ventilator or the A/C?

share|improve this question
What kind of car (year/make/model) are you trying to do this on? As far as I know, you'd have to wire the controller separate from the ignition or the OBD-II system, as the temperature control is completely autonomous. – Paulster2 Jun 17 '14 at 23:00
I was hoping to build a generic product compatible with most brand but i going to test it on a VW Golf 2005. OBDLink MX claims it allows remote start-up. – arjang27 Jun 19 '14 at 13:59
On a VW, the key needs to be present. If it isn't, the immobilizer will prevent the car from starting. – Lynn Crumbling Jun 20 '14 at 13:11
@LynnCrumbling, I think there is a way to bypass immobilizer but how OBDLink MX can start-up the car without any wiring? and how to get the manufacturer specific OBD-II, do i need to reverse engineer the CAN messages? – arjang27 Jun 22 '14 at 12:38
@arjang27 bypassing immo is kinda hard, it can be done in software by flipping some bits in the engine ECU's ROM, but that is definitely a bad idea to turn off a security feature like this and may get you in trouble with your insurance if the car gets stolen. Moreover, you'll also need to reverse-engineer the protocol that the A/C's ECU uses to talk, which is way harder than the immo bypass. – user5106 Jul 17 '14 at 7:01

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.