Is this when you press the brake pedal ? If yes :
New Body style 2004 F-150
Check the BPP ( Brake Pedal Position ) Switch for the shift interlock circuit.Use a meter to a known good ground to the wire in the connector :
Fuse # 16 is the Tan w/ Red Stripe wire to the switch Should be hot in run or start positions
Pink w/ Light green stripe wire should have 0 V DC with the brake pedal off. When you press on the brake pedal, this wire should have + VDC.
The BPP is mounted to the brake pedal lever, low with 4 wires to it ( the other 2 wires are for the brake lamp circuit ).
If you have power on both sides of the BPP with the pedal pressed down, the next 2 things are the solenoid ( part of the ignition switch ) or the shift interlock itself.
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