P0406 Fault Code

Exhaust Gas Recirculation Sensor A Circuit High

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0406 fault code indicates that there is a problem with the Exhaust Gas Recirculation (EGR) sensor A circuit, specifically that the voltage reading is higher than expected. The EGR system is crucial in reducing nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the intake manifold, which helps to lower combustion temperatures.

What are the symptoms of the P0406 code?

When a P0406 code is present, you may experience:

• Illuminated Check Engine Light (CEL).
• Poor engine performance or rough idling.
• Increased emissions and potential failed emissions tests.
• Decreased fuel efficiency.

What causes the P0406 code?

Several factors could contribute to the P0406 code. Common causes include:

• A malfunctioning EGR sensor.
• An open or short circuit in the EGR sensor wiring or connectors.
• A faulty EGR valve that is stuck or not operating correctly.
• Engine control module (ECM) issues that misinterpret the sensor data.

How to fix P0406?

To resolve the P0406 code, follow these steps:

1. Inspect the EGR sensor and wiring for any signs of damage or corrosion.
2. Check the EGR valve operation to ensure it is functioning properly.
3. Use a multimeter to test the voltage at the EGR sensor to confirm it is within the manufacturer's specifications.
4. Replace the EGR sensor or valve if they are found to be faulty.
5. Clear the fault codes and conduct a test drive to ensure the issue is resolved.