OBD-II Code · Emissions
P0407
EGR Sensor B Circuit Low
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$100–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Secondary EGR position low.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Likely causes
- Failed sensorMost common
- Wiring
Read the full diagnostic procedureP0407 means the EGR position sensor B signal is reading low — same fault mode as P0405 but on the second of two position sensors used on EGR valves w…
P0407 means the EGR position sensor B signal is reading low — same fault mode as P0405 but on the second of two position sensors used on EGR valves with redundant or dual-feedback designs. Dual-sensor EGRs are common on modern emissions-strict platforms (post-2010 Ford, Mazda, some VW/Audi TDI) where the ECM cross-checks two independent position signals to satisfy OBD-II rationality requirements; if either signal disagrees with the other or drops out of range, the ECM throws the corresponding A or B code.
Diagnostic ladder is identical to P0405
- backprobe the B-signal pin with the connector seated and read at-rest voltage (spec typically 0.6-0.9V closed); unplug and verify 5V reference and ground; check signal-wire continuity from connector to ECM for chafe or open.
- The added wrinkle on dual-sensor valves is that you can have one sensor failed and one healthy — the ECM will still throw P0407 even though the valve still reports position accurately on sensor A. On diesel applications (Cummins 6.7L, Powerstroke 6.7L, Sprinter OM642), soot contamination inside the EGR valve assembly can short the B-signal trace on the sensor PCB to chassis ground through wet soot — cleaning rarely fixes it, the assembly replaces.
Vehicle-specific patterns2011-2016 Ford 6.7L Powerstroke throws P0407 from soot contamination of the dual-position-sensor EGR valve — the valve assembly is $400-$700 and is t…
- 2011-2016Ford 6.7L Powerstroke throws P0407 from soot contamination of the dual-position-sensor EGR valve — the valve assembly is $400-$700 and is the only repair; cleaning attempts fail because the soot conducts.
- 2007-2014Cummins 6.7L (Ram 2500/3500) throws P0407 from the same dual-sensor soot pattern — valve replaces with a Cummins-branded service kit.
- 2010-2014VW/Audi 2.0L TDI (CBEA, CJAA engines) throws P0407 from internal EGR cooler failure routing soot into the position sensor cavity; the cooler and valve replace together.
- 2012-2016Mercedes Sprinter OM642 3.0L V6 diesel throws P0407 from a known EGR actuator failure with a Mercedes TSB and extended coverage — verify VIN before quoting out of pocket.
Estimated repair$200 (light-duty valve) to $1,400+ (diesel EGR valve + cooler).
Look up another code
P0407 — frequently asked
What does a P0407 code mean?
Secondary EGR position low.
What causes a P0407 code?
Common causes: Failed sensor; Wiring.
What are the symptoms of a P0407 code?
Typical symptoms: Check engine light.
Is it safe to drive with a P0407 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $100-$400.
How do I diagnose a P0407 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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