OBDII Port code

[william.buchanan]

Hi all

Has anyone out there got experience of communicating with the OBDII port on a vehicle?

I have seen a couple of things online but none seem to work. Also struggling to work out how to communicate with the cable via USB.

Any guidance appreciated….

 

[william.buchanan]

Does it show as a USB device with a yellow warning icon? Or as a normal icon? If it's a normal icon what is the device driver associated with it?

Ok, this is a bit strange. It is actually showing up under Ports (COM and LPT). It has named it USB-SERIAL CH340 (COM5). It seems to be using a driver from winchiphead.com. I have no idea where that came from - possibly one of the things I installed while trying to get this going. I tried removing that driver and deleting it from the system32\drivers folder but it just keeps reappearing.

 

[Skydiver]

Try connecting to COM5, treating it as a serial port.

 

[william.buchanan]

Try connecting to COM5, treating it as a serial port.

Sorry - took me a while to get back to this.

So, I have a bit more information...

When I plug in the cable it seems to load as COM5 using the driver CH341S64.sys from winchiphead.com (no idea where that driver came from - probably an early attempt to get it working).

I have downloaded some code which sends a couple of init commands followed by requests for Engine RPM, Vehicle Speed, and Fuel System Status.

When I try sending commands, what I am seeing is that all the commands are just echoing back to me. So the output says 'sending 010D', followed by 'received 010D'. It does this for all commands.

If I unplug the cable from the OBD port but leave it plugged in to the USB Port, then it freezes when going through the init - so that tells me it must realise it's not connected to the car.

Also, I tried to communicate using power shell. I got the same result - i.e. all the commands echoing back to me.

What do you think? Is this a driver issue or cable issue? Or something else?

Thanks

 

[Skydiver]

Sounds like the cable to me, but I am way out of my depth here.

 

[JohnH]

I have no idea about the issue in particular, but your last post reminds me of when I was testing some code for serial port years back, and used a paper clip to short pins 2 & 3 effectively creating a loopback on the port - like this: https://desk.zoho.com/portal/factorywiz/en/kb/articles/paperclip-loopback-test

 

[william.buchanan]

Sounds like the cable to me, but I am way out of my depth here.

No problem. Thanks for your help so far. I am coming to the same conclusion... In fact I just ordered a different cable so will see if that works better.

 

[william.buchanan]

I have no idea about the issue in particular, but your last post reminds me of when I was testing some code for serial port years back, and used a paper clip to short pins 2 & 3 effectively creating a loopback on the port - like this: https://desk.zoho.com/portal/factorywiz/en/kb/articles/paperclip-loopback-test

You know - it kind of has that feel about it, as if there is some kind of loopback built in to the cable... I have just ordered a new cable so will soon know if this was the problem. Thanks

 

[william.buchanan]

So, just to update on this... I bough a new cable; plugged it in; ran the code - everything worked perfectly!!!

I'm kind of annoyed at all the lost time with the last cable, but relieved that it's working now!

Thanks for the advice along the way folks...

 

[Skydiver]

Woo hoo! Congratulations!