Build your own OBD11 Code reader.

tblo760 · Post by **tblo760** » 16 Jul 2010, 18:56

As you all know the 200 & 700 series had a diagnostic/code reader under the bonnet (hood) The 850s and similar models have an OBD11 Socket inside the car,usually under the ash tray.You can easily read and re-set the fault codes with a simple little circuit,the attachment shows how to do this.Allthough it's quite acceptable to simply insert the wires into the socket,I made a very neat little unit on a small peice of strip board and fitted it into an old key fob,I also obtained an OBD11 plug (ebay) to make a permanent set up that I simply plug in (which means I don't have to put my spectacles on) I've used this many times to read and re-set codes,I even managed to reset the ABS fault code,which can be a real problem,in fact I know a garage that paid £4000 for a computerised set up,and they failed to reset the ABS light,so I lent them mine.Good luck.

: OBD11 code reader.JPG (27.96 KiB) Viewed 10240 times

SORRY ! I should have gone to specsavers,I've made a mistake on the attachment,pin #3 is chassis ground not 4.The reason for this error,is I've got 2 types of OBD11 Plugs,one is just the basic plug where all the pins are seperate,the other has the pins mounted on a small circuit board and there is a jumper between 3 & 4. So the configuation is 3=Grnd, 5=Signal Grnd,16=+.
With regards to resistors and LEDs,1st you must find out the voltage rating of the led,most 1.7 & 2,2 v leds will run quite happily on 3 volts.You can try testing leds using 1.5v batteries to see what voltage you need to light it up,or set your multimeter to continuity which will supply the led with 3 v,The positive lead on the led is allways the longest to identify the polarity,if it's connected the wrong way,it won't light but will not harm the led.The rating of the resistor will 1st stop the led from 'frying' and also govern the brightness required.1k2 to 1k8 ohms should be ok for these leds.

Kuhnman · Post by **Kuhnman** » 16 Jul 2010, 21:15

Do you know if this would work with a 98 V70xc? I'm thinking not, my plug is in the centre console and I think the OBD 2 system is a bit different. Worth asking though. I bough a MAC tools code reader for $60 Canadian but it only gives me emissions codes, not ABS or body module codes. Thanks!

Post by **thecheat** » 16 Jul 2010, 22:18

I can't seem to figure out how to subscribe to a thread without commenting so.. hi!

I have made a circuit just like this to get the mileage out of the instrument cluster but it isn't working. I used a 1.5kohm resistor for my led - could that be the problem? It works on the ECU pin but not on the instrument cluster pin 7.

I may have to go out to the store and see if I can get the right resistor and try again.

tblo760 · Post by **tblo760** » 22 Jul 2010, 05:28

I have only had access to 850s,850Ts & 850Rs,so I'm not sure which other models have the same configuration,I have successfully read and cleared fault codes including ABS and Limp mode faults,it does work.

Post by **cn90** » 22 Jul 2010, 08:56

Very clever, I like it but.....

In the USA, I can buy an Actron brand OBD-II code reader for US $45.00.
So although this is interesting, I cannot see myself making this OBD tool!

Post by **vjaneczko** » 22 Jul 2010, 15:22

I have a '97 855 which does not have the diag box near the ECU If I'm reading this correctly, this will give me the same funtionality, right? I have the Actron reader but it doesn't give me EEC codes; just the ODBII codes. Will this behave just like the diag box on older cars?