Long story short, I am finally seeing the light at the end of the tunnel on my car. It has been in the works for the past 3 years. For mods, looking in my sig. Anyway, I put a new battery in the car and was going to hook up my fuel pump relay and use the 12v switched wire from the ZEMS to activate the relay. When I recieved my ZEMS for an S4 it had no markings on the switched 12v loose wire. There are 2 wires that come loose, one for 12v switched and one for WBO2 input. My problem is that when I hooked a DMM to either wire, there was no voltage being shown on my multimeter, with or without the key on. Is there something I am not figuring? The car has a stock engine harness that is in great condition. Am I missing something here? All 3 of the lights on the megasquirt come on when I turn the key...

 

Open the connector and see which wire connects to pin 37.

Or go into output test mode, turn the fuel pump on and see which one of the wires switches ground when you turn the fuel pump on and off in test mode.

 

So, correct me if I am wrong but this is a fuel pump ground and not a switched 12v?

 

Fuel pump relay is controlled by opening and closing ground.

 

One other way to test would be to use a test light, but instead of attaching the test light's clip to ground, attach it to +12v and then probe the wires while in test mode. The resistance of the bulb should be enough to prevent any harm to the MS circuitry should you probe the wrong wire.

 

One of the wires should've been marked. The documents we sent with the unit should've had a note on which wire to use for what.

 

^The wire was not marked when I had recieved it, it is no biggy I will just check continuity with ground is all with my DMM.

 

We used a sharpie marker to mark one of them... we did this to all of the adapters.

If you somehow got one that didn't have the mark, I guess it could've wiped off, although the marker was supposed to be permanent.

Ken