P0407
EGR Sensor B Circuit Low
EGR / emissions
Generic OBD-II
Medium
What it means
P0407 means the signal from EGR sensor B is reading below its valid range. This sensor reports how far the exhaust gas recirculation valve is open (or its temperature), letting the computer control EGR flow for lower emissions. A low signal usually points to the sensor, its wiring, or a poor connection, and mainly affects emissions rather than the ability to start or drive.
Medium
Can I keep driving? You can keep driving. You may notice slightly rough idle or hesitation, but this emissions-circuit code won't cause a no-start.
Common symptoms
What you'll notice
- Check-engine light on
- Slightly rough idle or minor hesitation
- Reduced fuel efficiency
- Failed emissions test
Common causes
Most likely first
- Faulty EGR position/temperature sensor B (signal reading low)Likely
- Wiring shorted to ground or an open in the signal circuitCommon
- Corroded or loose sensor connectorCommon
- Failed ECM (rare — check the sensor and wiring first)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the fault is on the EGR 'B' sensor circuit.
- Inspect the sensor connector and wiring for a short to ground, corrosion, or loose pins.
- Check the sensor's reference voltage and ground back to the ECM.
- Measure the sensor's output and compare it against spec across its range.
- Replace the EGR sensor if its signal stays low, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0407?+
Generally yes. It's an emissions-related fault, so you may see slightly rougher running, but it doesn't stop the engine from starting. Repair it to pass emissions and keep EGR working properly.
Can I just clear P0407?+
It will return until the sensor or its circuit is repaired, and the car will not pass an emissions test with it pending.
Related codes
Often seen with P0407
Read & clear P0407 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX