P0408: Exhaust Gas Recirculation Sensor B Circuit High

What does P0408 mean?

P0408 is a diagnostic trouble code indicating "Exhaust Gas Recirculation Sensor B Circuit High". The ECU is reading a voltage that is above the expected range. This can be caused by a short to power in the wiring, a failed sensor, or a connector issue in the egr system.

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 egr system sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

This code sits in an engine peripheral, typically emissions or forced induction. It will not take braking or steering away, but it can put the car into limp mode, cost you fuel and fail a roadworthy. Book it in rather than clearing it and hoping.