Playing with the OBD-ii... got the mileage?

takane2 · Post by **takane2** » 07 Aug 2012, 05:23

For each press after the first 5 are you waiting for the light to go off then back on as mentioned here? https://www.matthewsvolvosite.com/forums ... php?t=6731? If I recall the first 5 have to be held down for a bit.

Has anyone other than me been able to get this to work? From the other posts it seems like I've been the only one to get the mileage. If I still had an 850 I'd make a video. If anyone in my area is willing to let me try this on their 850 I'd be down.

schmuecker · Post by **schmuecker** » 07 Aug 2012, 16:41

I don't even get the light to turn on no matter how many times I press the button. So it's not a matter of waiting for it to go off...

schmuecker · Post by **schmuecker** » 08 Aug 2012, 13:08

I tried again, different length pushing the button and also switching around pin 5 and 7. Pin 5 is for signal ground per link below and Pin 7 for K-Line. I'm not an electrical engineer, but I thought I just try around. When switching it around, the light is on all the time, I then tried pushing the button (applying current to Pin 7) but still nothing happens. It's puzzling to me, because if it did work on you '97 and it's using the same protocol as my '98 so not sure why it wouldn't work at least for the trouble codes (one 1-second push I believe).

http://pinoutsguide.com/CarElectronics/ ... nout.shtml

takane2 · Post by **takane2** » 08 Aug 2012, 17:30

When you have the switch on pin 7, you have a complete circuit for current to flow from power through the LED and then to ground all the time. You will still be switching pin 7 but you would never see the output.

With the circuit in my diagram, closing the switch pulls the input to ground and completes the LED's circuit giving you feedback. When open
When pin 7 is acting as an output the switch is open, so when pin 7 is high no current flows and the LED is off. This is because both sides of the LED are at the same voltage with reference to ground. When pin 7 is low the current flows from the higher voltage from pin 16 to the lower voltage on pin 7. This lights the LED.

So you connect the circuit. Press the switch 5 times, wait for the light to come on etc as described in the procedure for getting the mileage from obdI, just using the circuit instead of the diag box. Maybe it doesn't work on V70s? What kind of LED and resistor are you using?

schmuecker · Post by **schmuecker** » 09 Aug 2012, 10:28

Thanks for the tutorial

I used the following - That's what is writte on the packages.

RadioShack 5mm Red LED, 12VDC, 20mA, 1.5mcd
RadioShack 1k-Ohm Metal-Oxide Resistores, 1 watt, 5% tolerance
SPST Momentary Submini Pushbutton Switch - Contacts rated 0.5A at 125VAC/250VAC. In testing it with just Ground and Power, I figured out that it is always open (LED came on when I pused the button)

Did i get the wrong parts?

takane2 · Post by **takane2** » 09 Aug 2012, 16:21

Is that LED part number 276-209? Radio shack doesn't list specs but according to a review it has an internal resistor(probably why it is so expensive). I assume it is since it is unusual for an LED to be given a voltage rating like that.

schmuecker · Post by **schmuecker** » 11 Aug 2012, 00:52

I'll have to check - i left the stuff at work so won't be able to reply until Monday. Are you saying that if it does have a resistor included, I won't need the 1k resistor and just take that out and try it? If I'm not at risk of frying the car's electronic, I can certainly try that, maybe that's why nothing was happening because the current was too low for the K-Line to transmit anything to the car computer?

schmuecker · Post by **schmuecker** » 13 Aug 2012, 11:12

So yes, the part number is 276-0209. and i now also saw that it says "with integrated resistor" underneath the ratings. I forgot to post that earlier. Sounds like I should go ahead and test the same thing without the resistor then, right?

takane2 · Post by **takane2** » 13 Aug 2012, 19:39

Yes, it should be fine. Does the packaging have any other specs listed on it? As long as it doesn't pull more than 20mA it's good.

schmuecker · Post by **schmuecker** » 23 Aug 2012, 18:09

I tried playing around with it some more still not working....

Turns out I bought a 1995 Volvo 850 turbo, where I could verify the mileage under the hood (it worked great). My home-made electronic thing was meant to be used if I bought a 1996 or younger...

Even on my "new" 1995 Volvo I couldnt' get it to work via the OBD-II i.e. with the breadboard, so I figured I am doing something wrong here. Not a big deal as I won't need it anymore...

Playing with the OBD-ii... got the mileage?

Re: Playing with the OBD-ii... got the mileage?