Error code · Engine

P0406 — Exhaust Gas Recirculation Sensor "A" Circuit High

Safe to drive

A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.

Possible causes

What you can do yourself

  1. The position sensor is usually built into the EGR valve; a differential pressure sensor sits nearby and is connected to the exhaust by two tubes. Check the connector and the tubes for cracks or soot blockage.
  2. Usually the car drives as before; a diesel may go into limp mode with weak pull.
OOleg’s tip: check the connector

Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.

Unplug and inspect connectors with the ignition off.

Find the part on Kaspi ShopBefore buying, check the part number or match the part by VIN in the Kaspi “Garage”.

The explanation comes from the error code reference in the AvtoElektrik PRO app.

Need a mechanic’s help?

Couldn’t fix it yourself? Oleg, an auto electrician, does computer diagnostics and repairs: he comes out anywhere in Almaty or sees you at his workshop.

Want to figure it out yourself?

Oleg’s course “Car computer diagnostics with a scan tool”: how to hook up a scanner, read codes and live data, and use them to find the cause. The first lessons are free.

Scan tool diagnostics course →

Nearby codes

All codes in P04xx →

Who keeps this reference

The reference is kept by Oleg Dmitriev, an auto electrician from Almaty with 26 years of experience: computer diagnostics of cars and trucks, repair of control units (ECUs). Can’t find the cause? Message him.