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Old 10-01-2009, 11:19 PM   #20 (permalink)
EcoModding Lurker
Join Date: Jun 2009
Location: Phoenix
Posts: 87

pickup - '01 Dodge Dakota Quad Cab 4x4 Sport
90 day: 16.35 mpg (US)

Focus - '16 Ford Focus SE
90 day: 31.46 mpg (US)
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Bullydog Watchdog and OBDII current

SVOboy, did you ever get a chance to try the Watchdog out?

Originally Posted by cfg83 View Post
bluetwo -

I think you answered your own question. I think that the price of "plug and play" is that it is using what the OBD II spec is giving to it. I went looking for the volt/amp out of OBD II and found this :

16 pin car OBD2 special connector diagram and applications @

OBD II to USB cable pinout and wiring @

Question: Can someone interpret the juice coming in from the above schematic?

I went to my car and tried to measure the amps of pin 16 but I messed up. I blew a fuse, not good! Sooooo, I do not suggest that you try this unless you know your electronics (I obviously don't, ).

cfg83, that circuit will draw between 10 and 11 milliAmps at the voltages shown. At a more typical 13.5VDC battery voltage it will draw close to 12 mA. The actual maximum current rating of the PCM at pin 16 is probably out there. Somewhere.

You should NEVER try to measure the current (Amps) of an open circuit with your multimeter. It is designed to measure current in series with a device or electrical load. That's why you blew a fuse. The meter in the Amps position will have no (or very little) resistance and act like a dead short. If you do that on an unfused circuit, or even a fused one with enough potential you will ruin your multimeter. Sometimes catastrophically.

The fuse that blew might be a clue to the maximum current ability of the PCM at the OBDII port. Which fuse was it and what was it's rating? If it was a fuse on the car, the safe rated current for the OBDII port is 75 to 80% of the rating of the fuse that blew.
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