P0406: EGR Sensor A Circuit High
The P0406 code indicates that the Engine Control Module (ECM) has detected a high voltage signal from the Exhaust Gas Recirculation (EGR) position sensor 'A' circuit. This sensor monitors the position of the EGR valve pintle. A high voltage reading typically means the sensor is stuck at a high reference voltage or there is a short to voltage in the wiring. This can cause improper EGR flow, leading to driveability issues and increased emissions.
01. Most Common Causes
- Faulty EGR position sensor
- Short to voltage in EGR sensor wiring
- Corroded or damaged EGR sensor connector
- Failed ECM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or engine stalling
- Poor acceleration or hesitation
- Increased fuel consumption
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect EGR valve and sensor connector for damage or corrosion.
Step 3: Test EGR sensor voltage with a multimeter; compare to manufacturer specs.
Step 4: Check for shorts or opens in the wiring between sensor and ECM.
Step 5: If sensor and wiring are good, test ECM output signals.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive long distances with P0406, as it can cause poor engine performance and increased emissions. Short trips may be okay, but have it diagnosed promptly.
How much does it cost to fix?▼
The cost to fix P0406 typically ranges from $50 to $150 for parts and labor, depending on whether the sensor or wiring needs replacement.