What Does P0407 Mean?
The EGR (Exhaust Gas Recirculation) position sensor B circuit is reporting a low voltage signal. On systems that use a secondary or redundant EGR position sensor (sensor B), this code indicates the sensor B signal is below the ECM's expected minimum threshold. Despite the description mentioning 'high,' P0407 is officially defined as the EGR sensor B circuit low condition. The driver may not notice immediate drivability symptoms, but EGR monitoring will be compromised.
Common Causes
30%
Failed EGR position sensor B with low voltage output
30%
Signal wire shorted to ground in the sensor B circuit
20%
Corroded or water-damaged connector at sensor B
12%
Open or damaged 5V reference supply to sensor B
8%
ECM sensor B input circuit failure
Diagnostic Steps
1
Identify the EGR sensor B connector (separate from sensor A) and check the voltage PID — should read 0.4–0.9V at rest. A reading near 0V confirms the low circuit condition.
2
Disconnect sensor B connector and measure the reference voltage (should be 5V) and ground (should be near 0 ohms to chassis ground) at the harness side.
3
Check the signal wire for shorts to ground — with the connector disconnected, measure resistance between the signal pin (harness side) and chassis ground. Should read OL (open).
4
Inspect both the sensor-side and ECM-side connectors for corrosion, water intrusion, or damaged pins.
5
If the 5V reference is missing, check if other sensors on the same reference circuit are also affected — a shared 5V reference failure can set multiple codes.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
The EGR (Exhaust Gas Recirculation) position sensor B circuit is reporting a low voltage signal. On systems that use a secondary or redundant EGR position sensor (sensor B), this code indicates the sensor B signal is below the ECM's expected minimum threshold. Despite the description mentioning 'hig...
The most common cause of P0407 (Exhaust Gas Recirculation Sensor A Circuit High) is: Failed EGR position sensor B with low voltage output
Typical repair costs for P0407 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. Sensor B is typically a secondary feedback sensor. The ECM may rely on sensor A for EGR control. Emissions monitoring will be incomplete and the vehicle will fail emissions testing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0407 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / EGR System
Difficulty
Type
Generic (SAE)
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