All codes
P0407Emissions System
Exhaust Gas Recirculation Sensor B Circuit Low
P0407 means the EGR position sensor B signal is below the expected electrical range. Learn what to check before replacing parts.
What you may notice
Symptoms
- 01Warning light may illuminate
- 02Intermittent or implausible scan data
- 03Vehicle-specific symptoms may vary
Where to look first
Common causes
- 01A short to ground, lost reference voltage, damaged connector, or EGR position sensor fault can pull the signal low.
- 02Wiring, connector, or ground fault
- 03Vehicle-specific mechanical or control issue
A sensible sequence
Best diagnostic order
- 01Save codes and freeze-frame information
- 02Identify the EGR system used on this vehicle and verify reference voltage, ground, signal, and connector condition before replacing parts.
- 03Confirm readings with vehicle-specific specifications
- 04Verify the repair under the conditions that set the code
Step by step
What to check and repair
- 01Identify the EGR system used on this vehicle and verify reference voltage, ground, signal, and connector condition before replacing parts.
- 02Repair only the verified cause and retest
Read the signals
Live-data clues
Related sensor or switch signal
- Typical behavior
- Plausible and consistent with the operating condition
- Possible clue
- An unexpected value or dropout helps localize the fault
| Parameter | Typical behavior | What it can suggest |
|---|---|---|
| Related sensor or switch signal | Plausible and consistent with the operating condition | An unexpected value or dropout helps localize the fault |
What P0407 means
The EGR position sensor B signal is below the expected electrical range. The code identifies an observed condition; it does not prove which part needs replacement.
Diagnostic direction
Identify the EGR system used on this vehicle and verify reference voltage, ground, signal, and connector condition before replacing parts.
Before clearing the code
Save stored and pending codes and freeze-frame data. Use service information for the exact vehicle before repair, then confirm the issue no longer returns.