P0407: Exhaust Gas Recirculation Sensor B Circuit Low
What to do
Usually driveable with no symptom beyond the warning light.
What this code means
The second EGR position sensor is reading below its plausible range. Engines that recirculate through two paths, or that use a dual-feedback valve for finer control, carry a second sensor designated B — the diagnosis is identical to sensor A, applied to the other circuit.
When A and B faults appear together, suspect a shared ground or reference rather than two failed sensors. Two sensors failing in the same direction at the same moment is far less likely than one wire they both depend on.
Likely causes
Start here
- Faulty EGR position sensor · easy
- Signal wire shorted to ground · moderate
- Corroded or loose connector · easy
Less common
- Failed sensor reference voltage supply · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0407.