How much does it cost to fix P0405?

DIY repair typically costs $15–$130 for parts. Professional repair runs $200–$500 including parts and labor.

P0405

Powertrain

Moderate

Exhaust Gas Recirculation (EGR) Sensor A Circuit Low

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The P0405 code indicates the Engine Control Module is receiving a lower-than-expected voltage signal from the EGR valve's position sensor (Circuit A). The ECM uses this sensor to determine the exact position of the EGR valve and verify that it's responding correctly to commands. When the voltage drops below the manufacturer's minimum threshold, this code is triggered.

You'll likely notice a Check Engine Light along with rough idle and possible engine knocking, especially under load. The engine may feel less powerful because the ECM may default to a safe operating mode when it can't accurately determine EGR valve position. The vehicle will also fail an emissions test.

Diagnosis should begin with inspecting the electrical connector at the EGR valve for corrosion, bent pins, or moisture intrusion. Using a multimeter, check the signal voltage at the sensor—it should typically read between 0.5V and 4.5V. If the voltage is near 0V, trace the wiring for shorts to ground. On many vehicles, the sensor is built into the EGR valve and cannot be replaced separately, requiring a complete EGR valve replacement. Professional repair typically costs $200 to $500.

Severity

Moderate — Address SoonThis Week

Symptoms

•Check Engine Light is on
•Rough or erratic idle
•Engine pinging or knocking during acceleration
•Noticeable loss of engine power
•Poor fuel economy
•Failed emissions inspection

Likely Causes

Faulty EGR position sensor35%

The EGR valve's position sensor has failed or degraded, outputting a voltage below the normal operating range.

Wiring short to ground in EGR sensor circuit25%

A wire in the EGR sensor circuit has become grounded due to chafing or damage, pulling the signal voltage abnormally low.

Corroded or damaged EGR valve connector20%

Corrosion or physical damage at the EGR valve's electrical connector creates high resistance or an intermittent ground, producing a low-voltage reading.

Failed EGR valve with integrated sensor15%

On many modern vehicles, the position sensor is integrated into the EGR valve. A valve failure can produce low sensor voltage readings.

ECM ground circuit issue5%

A poor ground connection at the ECM or in the sensor ground circuit can affect the reference voltage, causing a low reading.