OBD 2 Reader

[WilliamN]

Anyone know if there are Schematics for a DTC reader. Nothing fancy, I just want to be able to read the code and thats it. Incase anyone is wondering what I am talking about, OBD is the on board diagnostic computer that tells you whats wrong with your car when the engine light comes on.

 

[panic mode]

If you are just fixing your own car, go to www.batauto.com
They have detailed instructions how to obtain and interpret
the trouble code from just about all cars.
If you want to build interface for some project, you will
have to specify protocol (J1850, ISO9141, ISO9141, LIN, PWM...).
I made couple of ODB2 interfaces for ISO9141 and wrote program
in VB for communication with ECUs for Honda.
Note that most of the cars out there will talk ISO9141 (all European,
all Asian and ca. half American).
Here is very simple schematic that doesn't use special parts.
You don't need to worry about L-line so you can even simplify it
if you want to (I always used only K-Line).
The circuit is plain level shifter designed probably by some Russian
guy (the website I found it looked Russian to me).

 

[stevez]

I'm just starting to learn about OBD II as two of my three vehicles have that interface available. Also learning that the ABS system that I have on one of the vehicles requires a separate instrument - or at least that's where I am coming out. Any help on Do_It_Yourself approaches to ABS diagnostics would be appreciated. Wiring harness and wheel sensors aren't that hard to replace -having access to the diagnostics would save some time.

 

[panic mode]

Here is another interface which sports optical isolation but uses
control lines so programming is a bit more complicated.
http://www.planetfall.com/~jeff/obdii/

 

[WilliamN]

OBD interface

Thanks for your help!

 

[alp60]

thank
panic mode..

new hex can protokol samples... ??

 

[RadioRon]

Best approach to get going quickly is to use an ELM chip (https://www.elmelectronics.com/) They make single chip OBD to RS232 transceivers that take care of protocol for you. You can also get simple kits of pcb plus ELM chip plus discretes from a variety of other vendors (you will need to google for examples but here is one **broken link removed**
). There are also many vendors with freeware or modest cost software that works with these ELM chips to give you a complete reader package for cheap.

 

[HiTech]

You can also use your instrument panel lamps to indicate the code(s). There are plenty of websites that tell you the flash code and its meaning. Harbor Freight Tools.com sells an OBDII digital readout scanner for dirt cheap. Easier to buy one than to make it. Now a programmer/reader is a whole different beast.