DTC P0406 Exhaust Gas Recirculation Sensor A Circuit High

In the complex world of automotive diagnostics, a solid understanding of On-Board Diagnostic Trouble Codes (DTCs) is crucial. Today, our focus is on DTC P0406, specifically the Exhaust Gas Recirculation (EGR) Sensor A Circuit High issue. In this comprehensive guide, we will decode the meaning of P0406, explore its potential root causes, examine the symptoms associated with this trouble code, outline a systematic diagnostic approach, and provide effective solutions for resolving this concern. Let’s dive into the intricacies of DTC P0406.

1. What Does P0406 Code Mean?

DTC P0406 is a diagnostic trouble code that indicates a high voltage condition within the Exhaust Gas Recirculation (EGR) Sensor A circuit. The EGR system plays a vital role in reducing emissions by recirculating a portion of exhaust gases back into the engine’s combustion chambers. When a high voltage condition is detected, the Engine Control Module (ECM) triggers the P0406 code, signaling an issue within the EGR Sensor A circuit.

2. What Are the Causes of DTC P0406?

To effectively troubleshoot DTC P0406, it’s crucial to understand the potential triggers behind this code. The underlying causes may encompass:

  • Wiring issues, such as damaged or corroded connectors within the EGR Sensor A circuit.
  • A malfunctioning EGR Sensor A or its related components.
  • A faulty EGR valve or position sensor affecting sensor performance.
  • An excessively high voltage supply to the EGR Sensor A circuit.
  • In rare cases, ECM-related problems affecting the sensor circuit.

Identifying the primary cause is the initial step toward resolving this high voltage condition.

3. What Are the Symptoms of DTC P0406?

Being able to recognize the symptoms associated with DTC P0406 is vital for early detection. Common indicators of this issue include:

  • An illuminated check engine light (CEL) on the vehicle’s dashboard.
  • Potential engine performance issues, such as reduced power and responsiveness.
  • Elevated exhaust emissions, potentially leading to a failed emissions test.

Addressing these symptoms promptly is crucial to prevent further complications.

4. How to Diagnose DTC P0406?

Accurate diagnosis of DTC P0406 requires a systematic approach. Here’s a step-by-step guide:

If initial inspections and basic testing do not pinpoint the cause of DTC P0406, consider employing advanced diagnostic tools, such as an oscilloscope, to assess the EGR Sensor A circuit more comprehensively.

5. How to Fix DTC P0406 Problem?

Once you’ve identified the underlying issue triggering DTC P0406, it’s time to address it effectively. Here are steps to consider:

  • Repair or replace any damaged wiring or connectors within the EGR Sensor A circuit.
  • Replace the malfunctioning EGR Sensor A or related components if necessary.
  • Ensure the voltage supply to the EGR Sensor A circuit is within the specified range.
  • Clear the trouble code using your OBD-II scanner after completing repairs. This step is vital for resetting the check engine light and confirming that the problem has been successfully resolved.

Conduct a road test to confirm that the issue has been rectified and that the check engine light remains off.


In this comprehensive guide, we’ve explored DTC P0406, the Exhaust Gas Recirculation (EGR) Sensor A Circuit High code. Understanding its significance, recognizing symptoms, identifying potential triggers, systematic diagnosis, and the importance of code clearing equip you with the knowledge to confidently address this issue. Whether you’re a dedicated automotive enthusiast or a seasoned professional mechanic, resolving such problems not only ensures cleaner emissions but also enhances your automotive expertise. Here’s to smoother and more efficient travels on the road ahead!