Exhaust Gas Recirculation Sensor B Circuit Low
What does P0407 mean?
The P0407 code means the vehicle's onboard diagnostic system has detected: Exhaust Gas Recirculation Sensor B Circuit Low. This is a moderate severity code.
Common Symptoms
- Check Engine Light illuminated
- Rough idle
- Poor engine performance
- Increased NOx emissions
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Faulty secondary EGR position sensor Very High
- Short to ground in EGR sensor B signal wire High
- Corroded or water-damaged sensor connector Moderate
- ECM input circuit fault for sensor B Low
Step-by-Step Diagnostic Procedure
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Identify which sensor is sensor B for your specific vehicle using service information
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Check sensor B voltage on a scan tool -- voltage below 0.3V indicates a low circuit fault
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Inspect the sensor connector for moisture, corrosion, or bent pins
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Check the signal wire for short to ground with a multimeter
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Verify 5V reference voltage at the sensor B connector
Frequently Asked Questions
Can I drive with code P0407?
You can drive short distances. The secondary EGR sensor fault may cause the ECM to run the EGR system in a default mode, affecting idle quality and increasing emissions.
What is EGR Sensor B?
Some vehicles with dual EGR systems or redundant sensors use a B sensor for additional feedback. Sensor B is typically the secondary EGR position sensor used for monitoring or verification.
Is P0407 common?
P0407 is less common than P0405/P0406 because not all vehicles use a secondary EGR sensor. It is more frequently seen on diesel trucks and heavy-duty applications.