Usually a sign of a bad ground. The sedan ground is on the driver's side mount for the trunk hinge. Not sure where the ground is in the wagon. Check the FSM It is behind the upper or lower trim on the left or right side. A wagon guy should know. Also look for trailer wiring that has been done wrong.
With no socket ground the brake and turn signal circuit path flows through the park light wires to a good ground in another part of the car. When you turn on the park lights there is no ground path and the lights stop blinking.
Last edited by Z09B4U; 09-08-2019 at 12:00 PM.