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njakts · 03-21-2011, 06:56 AM

I have a feeling I am missing something
first - I had obd2 reader laying around, that uses bluetooth for communication. I opened it up and noticed that it is using this exact circuit apart there is some Pic microcontroller in the place of ELM chip, could this pic be ELM's replica?:

but the Tx Rx lines are connected to bluetooth module. so I pulled out the bluetooth module and connected TxRx to arduino. took it to car, connected but it only shows Obduino security, a * is bouncing around and Rx light on the OBD reader blinks several times.
So arduino is trying to communicate, but does not hear any answer (tried to swap rx and tx pins, no use)? then the problem must be the replica of ELM chip.

second - had a look at my cars wiring and found out that OBD is using pins 4 and 5 and of course 16 for power then there is Pin 7 - ISO 9141-2 K Line, Pin 13, and Pin 14 - CAN Low (J-2284). and there is no Pin 15.

since the pin 7 is present, I can deffo say that my car has ISO protocol?
the car is year 2000 Lexus IS200.

third - since my car uses ISO protocol I can make this circuit and it should work?

schlorkist's image

and fourth - how is the communication happening? why it is showing this obduino security?
when it will go off?

03-21-2011, 06:56 AM	#634 (permalink)
njakts EcoModding Lurker Join Date: May 2010 Location: Latvia Posts: 39 Thanks: 1 Thanked 0 Times in 0 Posts	I have a feeling I am missing something first - I had obd2 reader laying around, that uses bluetooth for communication. I opened it up and noticed that it is using this exact circuit apart there is some Pic microcontroller in the place of ELM chip, could this pic be ELM's replica?: but the Tx Rx lines are connected to bluetooth module. so I pulled out the bluetooth module and connected TxRx to arduino. took it to car, connected but it only shows Obduino security, a * is bouncing around and Rx light on the OBD reader blinks several times. So arduino is trying to communicate, but does not hear any answer (tried to swap rx and tx pins, no use)? then the problem must be the replica of ELM chip. second - had a look at my cars wiring and found out that OBD is using pins 4 and 5 and of course 16 for power then there is Pin 7 - ISO 9141-2 K Line, Pin 13, and Pin 14 - CAN Low (J-2284). and there is no Pin 15. since the pin 7 is present, I can deffo say that my car has ISO protocol? the car is year 2000 Lexus IS200. third - since my car uses ISO protocol I can make this circuit and it should work? schlorkist's image and fourth - how is the communication happening? why it is showing this obduino security? when it will go off?