P0408 — EGR Sensor B Circuit High

P0408: EGR Sensor B Circuit High — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

EGR Sensor B Circuit High. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • Unstable idle, reduced power or higher emissions.

Possible causes

  • Faulty EGR sensor B or damaged wiring/connectors.

What to check

  • Inspect sensor B circuit and connectors for damage and corrosion.

Also written as: P0408-00, P040800, PO408 (some scan tools add the fault-type byte, e.g. -00).