P0406

Exhaust Gas Recirculation (EGR) Sensor "A" Circuit High

Car Fault Codes Emissions & exhaust

Can you still drive? Yes, normally

Who can fix it? Needs a workshop

Typical repair time 30 minutes – 3 hours

Typical cost SAR 100 to 1,800

What it means

The engine computer has detected that the EGR sensor signal is above its allowed maximum. This usually means an open ground or signal wire, a short to a voltage source or a failed sensor, so the valve position or pressure reading cannot be trusted.

Symptoms4

Check engine light on.
Often no clear driving symptoms.
The computer may disable EGR, causing light knocking under load.
Failed emissions test.

Possible causes5

Open ground wire to the sensor.
Open signal wire or a loose connector.
Signal wire shorted to a power wire or another voltage source.
Failed sensor, which is built into the EGR valve on many vehicles.
Water in the connector corroding the terminals.

How to diagnose5

Watch the sensor signal on a scan tool and compare it with the manufacturer specification.
Check the ground at the sensor connector.
Check continuity of the signal wire between the sensor and the computer.
Inspect the wiring for a short to a nearby power wire.
Move the wiring and connector while watching the reading to find an intermittent fault.

How to fix5

Clean corrosion from the connector terminals or replace the connector.
Repair the open ground or signal wire.
Repair the short to the power wire.
Replace the sensor, or the EGR valve if the sensor is built into it.
Clear the codes and confirm the reading is back in range.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a ground wire or connector fault, and rises when the whole EGR valve must be replaced because of its built-in sensor.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

What is the difference between P0405 and P0406?

P0405 means the signal is too low, usually from a short to ground. P0406 means it is too high, usually from an open ground or signal wire.

Do I need a new EGR valve?

Not before checking the wiring and connector, since many cases of this code come from a corroded connector or broken wire.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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