interfacing to automotive engine control unit (ECU)

[gizzmo]

I trying to figure out how I can access my car's ECU through a serial interface. My goal is to have a microcontroller connected to the ECU so that I can monitor some ECU inputs (door open/closed, engine running/off, etc) and also directly control some ECU outputs (sound horn, flash headlights). I'm not sure this is even possible, has anyone tackled this type of problem before ?
thanks,
Dave

 

[hemporer]

First,you should know the protocol thar your car uses;
and then learn relevant application layer, transmit the request frame to ECU;
finaly, receive the response frame from ECU.

 

[kimyonh]

Hi Gizzmo,
I think that Hempore's advise is true, however, You must know what kind of your automovies? There are many iflash softwares, you can down load, for examble: http://www.decselectronics.com/ecuflashtool.html, **broken link removed**

 

[GSM Man]

There are several different OBD electrical interfaces & protocols used in automobiles including:

• ISO 15765-4 (CAN)
• ISO 14230-4 (Keyword Protocol 2000)
• ISO 9141-2 (Asian, European, Chrysler vehicles)
• SAE J1850 VPW (GM vehicles)
• SAE J1850 PW
• M (Ford vehicles)
• ISO 15765
• ISO 11898 (raw CAN)
• SAE J1939

I've designed products that monitor and control automotive systems using several of these protocols and some of them can be very difficult to work with, and you have to be careful you don't jam your car's network.

Your best bet is to use an "ODB to UART" converter chip as your interface to the car's system. These chips handle all of the communications with the vehicle allowing you to concentrate on your applicaiton. A couple of chips I'm aware of are:

STN1110: https://www.obdsol.com/stn1110/​

ELM3xx:https://www.elmelectronics.com/obdic.html​