B1509: Flash To Pass Switch Circuit Short To Battery

What does B1509 mean?

B1509 is a diagnostic trouble code indicating "Flash To Pass Switch Circuit Short To Battery". The ECU is detecting a voltage reading that is below the expected range in the body electronics circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Intermittent warning lights
• Erratic gauge readings

Common causes

• Damaged or corroded wiring harness
• Loose or disconnected electrical connector
• Failed body electronics sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.