Problems reading fault codes with reader
 

So I've made myself a little fault code reader using the instructions I found on this forum and all was going swimmingly until it came to the fault codes to be read out and nothing happened, not even a 1-1-1.

So...what could be the issue?

It is a 1996 850 2.5 SE estate with what I believe is a 10v engine. In terms of the little reader I know the LED works because it illuminates fine but when I push the "dipper" wire in for 2 seconds and then release, the LED goes off but then nothing at all happens after, even if I wait a while. I tried with the ignition on position 2 to start with, then tested position 1 and also with the engine on all with the same result...nothing.

Any suggestions clever people? I should probably explain that I have the engine management light on so am trying to use the reader to help figure exactly what the issue is so that I can fix it.

Thanks :)

Where did you connect the flash code reader? What pins did you connect to?

16 - positive
3 - negative and one end of the dipper
5 - other end of dipper but just for 2 seconds or so

the LED lights up while the dipper wire is being dipped in number 5

Have you tried changing 3 and 5 round?

The other combination I have read is
16 - positive
6 - negative and one end of the dipper
5 - other end of dipper

This didn't work for my car but it does with others I know

Happy to give that a try. Will do it later on when its not a billion degrees and report back any progress. Thanks Mr 4x4.

Ok tried both of those without success.

I’m wondering if any of the following are possible:
Does there need to be a specific amount of oomph in the battery for this to work?
Could my car have a different system like the actual OBD one?
Have I done something stupid?!

Not sure what's going on, are you sure you wired it correctly? does the LED work?

I am going to take it all apart tomorrow and get my soldering iron out to make some better connections but yes I’m sure I made it right, the LED lit up ok when powered using number 16 and I think it was number 3 but yes the bulb is ok.

Got me bloody flummoxed it really has!

Pin ordering
 

I've copied and pasted this

OBD-II pin 16 (12v) -> DB9 pin 9
OBD-II pin 14 High speed CANL > DB9 pin 2
OBD-II pin 11 Low speed CANL > DB9 pin 2
OBD-II pin 6 High speed CANH > DB9 pin 7
OBD-II pin 5 Ground > DB9 pin 6 & 3
OBD-II pin 3 Low speed CANH > DB9 pin

From https://paul.sullivan.za.org/volvo-c...BD-II_CAN-bus/

It would seem your numbers don't quite match up? (assuming I've understood what you're trying tp do)

I can verify that using that pinout I get can data to my laptop (I've built plugs for both the high and low speed busses) on my 2010 C30

D