I have a plx m300 that im using with s300j on a jdm p72. Im using an obd2a-obd1 conversion harness also. What I did was run the power and ground directly off the conversion harness. I called up hondata and the tech there said not to run power and ground for anything off of what the ecu uses for power and ground. I personally dont see why it matters. I used the solder butt connectors they sell at napa and am recording .2 ohms resistance on each wire, about the same as before the wires were cut and soldered. The connection is clean and tight. My answer to the tech at hondata was "Wouldnt circuit will run in a parallel , so should it matter ?" And he just said "Trust me dont run anything off of there."
Has anyone done this ?

 

Yes there are people that have but perhaps the best approach here is to be safe rather than sorry. There are lots of other places to get a 12v ignition switched source.

 

yea i understand where your coming from. Im not arguing that, my question is why exactly is it safer ?

And also my main reason for doing it this way was basically because I did not want to touch the factory harness.

 

You can pull power directly from an empty port in your fuse panel without going into your factory harness. They say you shouldn't tap the ecu power source because it will take away power needed to drive things like your injectors etc which could potentially lead to a lean condition or other problems.

 

But its run in parrellel so it shouldnt affect that.. There should still be 12v before the load in each circuit.

 

Unfortunately I do not have a good enough understanding of electronics to say anymore, one way or the other but I'm in for someone who can answer this directly.

 

Just found this post in a search as I am trying to get my damn wideband to read correctly......

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lude98SH &raquo;</TD></TR><TR><TD CLASS="quote">But its run in parrellel so it shouldnt affect that.. There should still be 12v before the load in each circuit. </TD></TR></TABLE>

Just because the voltage is not changed by adding an additional component into the circuit doesn't mean that there is no change to the circuit......look up "current divider" in wiki and play with a few different numbers and you will see that adding a component in parallel affects the current going through all of the parallel legs. Basic circuit analysis.

 

dont piggyback units tell you to do this in the instructions ? Ive never used one just heard thats how they say to hook them up ?

 

yes they may not get the same amount of amperage because one may be a bigger load than the other. Thats what I gathered from that article. Correct me if im wrong.