We're working on a customer's car. Had to fix a bunch of janky wiring already. Fuse 15 (Alternator and Speed Sensor) keeps blowing.

I don't think it has a C115 connector as the TSB says to look for.

The car is using a brand new Rywire OBD2B chassis harness. So, I don't think it's damaged wiring.

Waiting on a replacement upstream O2 sensor. Current one is a mess. Saw that a short on the rear O2 (on stock chassis) can cause the Alt/SP fuse to blow. Unsure if this setup would act similarly with a short in the upstream.

Any suggestions on what to check for next? I'm at a loss.

Edit: Getting about 17-18 amps at the fuse. I hear a relay click somewhere underneath the dash when I touch the contacts with the multi-meter.