just curious if anyone knows what the two plugs on on the back of most b and d seires harness I did a swap in my car and my friends car and every time I see it I wonder what it is for.

 

They're not pointless.

 

Those are connector pins where you can test continuity to a wire. So you can test to see if the connector, harness, or wire has a fault.

If you pop those caps off you will see the cap is a connector from one wire to the other

 

Yes they splice several circuits together into one feed wire. For example the yellow and black wires that are the live wire on each of the fuel injectors.

It's kind of inconsistent though because there are also some branch junctions permanently soldered inside the harness.

 

The grey one is +12V distribution to the injectors and a few of the engine sensors - definitely needed.

 

so the only function of the two plugs is to test sensors?

 

eh kinda. Mk378 reminded me of the complete answer

Honda also would (mostly) not use T style solder joints to join wires. So where the ecu, tach, and cruise control read the vehicle speed sensor there is another small connector like that right before the ecu. So thats why if fuse 15 fails the alternator, oxygen sensors, and speed sensor dont receove 12 volts

So it's technically a branched connector plug that simplifies diagnositcs.

 

They act as "distribution" jumper....meaning one wire provides signal or power to the other wires. If you look on the driver side, you have one for the injectors.

 

that the union points. yellow ones are for your injectors, some are ground wires and I cant recall the others. typically when you want to use peak and hold injectors on your civic/integra this would be the easiest spot to add a resister box