[franko72]

the flat four is the standard wiring to most rear end brake, running lights , and turn signals. They are four wires That are all adjoined side to side in one strip. Seems to me that they were working before you pressure washed . did you wash under the rear bed? if so maybe you just disturbed a connection point to your wiring. have someone hold down the brake pedal while lightly pulling and tugging at some of the connection points at the wiring and see if the brake lights flicker. good luck.