Yes, this wiring harness is in the engine compartment. If you're looking at the engine from the front of the car, you'll see the air filter box on the left. Follow the black pipe towards the right. You'll see a large bundle of wires, enclosed in loom and electric taped solid. The white/yellow wire is in a smaller bundle of wires within the larger that goes down towards the ground after it exits the large bundle, to the left. It's not easy to get to; there is a TON of tape to cut through.
I metered the green wire at the ECU, but it didn't test properly. It read ~7 VAC constantly, regardless of RPM.
Good luck! I too had to work in the cold, but without the luxury of a garage.