Exhaust Gas Recirculation Sensor B Circuit Low
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.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $120 - $450 (parts and labor)
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What Are the Symptoms of P0407?
- Check Engine Light illuminated
- Rough idle
- Poor engine performance
- Increased NOx emissions
- Failed emissions test
What Causes P0407? (Most Likely First)
- 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
Can I Still Drive with P0407?
Short distances only. P0407 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
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.
What actually makes the computer set an EGR code?
The OBD II regulation requires the system to flag EGR when flow deviates from the manufacturer's specified rate — in either direction, too much or too little — by enough to push emissions past 1.5 times the FTP standards; and, where no EGR fault could do that, when there is no detectable EGR flow at all (Title 13 CCR 1968.2, section (e)(8.2)). Note that excess flow is a malfunction too, which is why an EGR code does not automatically mean a blocked passage. This is the threshold the monitor is designed around, not a description of your specific fault — the regulation says what the system must detect, not how to find it on your vehicle.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0407?
-
Identify which sensor is sensor B for your specific vehicle using service information
-
Check sensor B voltage on a scan tool -- voltage below 0.3V indicates a low circuit fault
-
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
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1968.2 (OBD II)malfunction criteria, section (e)
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
P0407 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Which Vehicles Commonly Get P0407?
- 2005-2016 Ford F-250 Super Duty
- 2006-2018 Dodge Ram 2500
- 2004-2015 Chevrolet Silverado 2500HD
- 2007-2017 GMC Sierra 2500HD
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