I can't speak to the 145 specifically, but my intermittent short in my 90 740 on one side's tail lamps led me to this conclusion:

It's better not to find the short, but the wire. Then replace that entire wire. If you can narrow it down to one specific section of that wire, you can run a shorter piece of wire, but it can be a lot of work to find an exact source of a short.

I am not sure the 145 has plastic disconnects like in the 80s and later cars, but if you can disconnect sections of the circuit to find the offending wire, that's what I would do. Even clipping the wire and leaving lots of room to reconnect it would narrow it down, but it isn't strictly necessary to do so.


Unless you have something cutting into your harness causing shorts in multiple circuits, there is no real benefit to finding the exact location of the short.

You wrote: "I have a short to ground, somewhere in the harness between the positive side of the pump and the auxiliary air valve connector, (in the yellow wire)."
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You have a B20 Engine with a K-Jet FI system. The AuxAir Valve's only function is 'idle control'. It is only Open when cold. The wires to it Heat the mechanical thermostatic spring that closes the valve as the engine warms up and brings the idle back to normal.

You can disconnect it and the Fuel Pumps will run and the engine will start and run. If the ambient Temp is above 65 degrees the valve will be in the 'closed' position and the engine will idle as normal, the heat from the engine will close the valve (it's mechanical) with or without the "heater" being connected.

Look elsewhere for the reason the pump fails to run.

Could you elaborate on how you determined the short circuit is in the wiring harness? Did a fuse blow? Did you disconnect the fuel pump and aux air valve when measuring for the short?

To answer you questions:
One: try to isolate as much of the wiring as possible by unplugging connectors, if you haven't already (and as suggested by Ron).
A good short circuit to ground will be hard to trace with a multimeter, the resistance is just too low and the resolution of the meter too poor to give you relevant readings when you get closer to the short.
Two: yes, but only if that wire is exclusively going between the aux air valve and the fuel pump, meaning no other circuits are connected to that wire in between.

Warren;

...not really enough info for any specific suggestions or recommendations...but I'd separate connectors and divide and conquer...note also that FuPu itself if locked from being stored dry, and not turning, will act as a "short circuit".

Good Hunting!