Wiring under the car for o/d is (1) to the solenoid, (2) to the 4th gear switch (stick shift), and coming from the shifter well.

Not likely that pressure washing would mess it up, unless you poke the nozzle under there and blasted away.

The O/D relay is mounted with a clip to the rail that is a dash support and runs from left of the glove box to just right of the igniton switch.

Access it by (1) removing the glove box, and (2) looking leftward. It's the first relay you see, just under the center air vent suctwork.

Good Luck,

Bob

:>)