P0406 – Exhaust Gas Recirculation Sensor A Circuit High

Meaning:

When the EGR sensor has had abnormally high voltage reading for too long, the P0406 happens
The P0406 is triggered when the EGR sensor has had abnormally high voltage reading for too long

EGR sensor has had abnormally high voltage reading for too long.

Main Symptoms:

  • Check Engine Light comes on
  • May surge when you drive
  • May stall intermittently
  • Vehicle may fail emissions

Possible Causes:

  • Defective EGR valve
  • Short or open in EGR wiring circuit
  • Debris build up in EGR valve and is holding it open

Diagnostic Steps:

  • Pull codes and freeze frame data
  • Visually inspect all wiring to EGR to ensure there are no shorts or opens
  • Using a scan tool, view EGR position during startup and while running to ensure its correct
  • Clear code and do test drive

Read More: Autel MD802: Full System Automotive Scanner Review