P0405 Code – Meaning, Causes, Symptoms (& How To Fix)

P0405 Trouble Code

What Does the P0405 Code Mean?

Code P0405 indicates a problem with the exhaust gas recirculation system. It is triggered when the PCM fails to detect some change in manifold air pressure when the EGR valve is activated. Some vehicles require several driving cycles before the fault code is triggered, while on some vehicles the “check engine light” lights up when the first sign of a change in the exhaust gas recirculation flow rate is received.

Definition: P0405 Code: Exhaust Gas Recirculation (EGR) Sensor Circuit A Low

Modern vehicles also use an EGR position sensor that monitors the open and closed position of the EGR valve. The information from the EGR position sensor is sent to the PCM, which then decides on the exhaust gas flow rate depending on how much the EGR valve opens. If the calculation of the PCM does not match the data sent by the sensor, the P0405 code is triggered.

P0405 Trouble CodeCheck Engine Light Illuminates

Engine Hesitation

Rough Performance
Damaged EGR Valve

Clogged EGR pathway

Faulty EGR position sensor

Damaged wiring
EGR Sensor shorted to ground

Loose terminals to PCM

Broken Vacuum line(If vacuum EGR)

Faulty MAP sensor

Carbon buildup on EGR Valve

Faulty DPFE (Differential Pressure Feedback EGR) Sensor
Inspect the wiring to EGR sensor and ensure the connection is secure

Replace EGR Valve

Replace EGR Position Sensor

Check the car battery

Check the voltage at EGR system

Check for a vacuum to EGR control solenoid

Clean EGR Position sensor

Fix Vacuum leak

P0405 Symptoms

Faulty Diesel Egr Valve

If the EGR sensor circuits are damaged and the P0405 code is triggered, you will not experience any particular problems while driving, apart from the slight decrease in acceleration and fuel consumption. However, some of the common symptoms you will experience include:

Check Engine Light Illuminates

The check engine light illuminates as soon as the PCM reading does not match with the function of the EGR valve.

Engine Hesitation

If there is an issue with the voltage, the ECM may open the EGR valve more than required, causing the engine to hesitate or the acceleration to drop.

Rough Performance

If the ECM does not receive correct information from the EGR position sensor, the EGR valve position will not be determined correctly, resulting in rough engine performance.

Possible Causes

The P0405 sensor can be triggered due to many reasons. The most common cause include:

• Damaged EGR valve
• Clogged EGR pathway
• Faulty EGR position sensor
• Damaged wiring
• EGR sensor shorted to ground
• Loose terminals to PCM
• Broken vacuum line
• Faulty MAP sensor
• Carbon buildup on EGR valve
• Faulty DPFE (Differential Pressure Feedback EGR) sensor

Possible Solutions

To repair the P0405 code, it is most common to first check the wiring and connection to the sensor and EGR valve before replacing or repairing other components. Here are some of the fixes you can try:

• Inspect the wiring to EGR sensor and ensure the connection is secure
Replace EGR valveIr?T=Askamastermec 20&Amp;L=Ur2&Amp;O=1
• Replace EGR position sensor
Check the car battery
• Check the voltage at EGR system
• Check for a vacuum to EGR control solenoid
• Clean EGR position sensor
Fix vacuum leak

How to Diagnose the P0405 Code?

Since the P0405 code indicates a circuit problem, you will need a specific EWD (electric vehicle diagram) corresponding to your vehicle model and a digital multimeter (DMM) to diagnose the fault code.

Always Connect a Car Battery Charger

Whenever you perform troubleshooting on your car, especially with the ignition on, there is a high risk that the car battery will be drained. In addition, your car displays additional error codes at low voltage, which makes things more complicated. It is therefore necessary to always connect a car battery charger when you are troubleshooting a problem in your car.

Connect the OBD2 Scanner

An OBD2 Scanner is an excellent device that reads the error code information. Most modern scanners have basic settings that allow you to check and compare the reading of certain components to determine if a replacement is necessary. With the scanner, you can easily inspect and verify the EGR functions. You can also use a multimeter, but most experts recommend an OBD2 scanner.

Check for Wire Connection

The first step is to check the wire connections and look for damage or burns that could lead to circuit problems. Also, look for possible water damage or bent and broken pins.

Inspect EGR Position Sensor

A traditional and most common EGR position sensor is a three-pin type with a reference voltage, ground and signal. If the EGR valve in your vehicle is vacuum actuated, perform the position sensor test using a vacuum pump and a DMM. Remove the connector and measure the resistance over the entire circuit. The measured value should be about 6 kΩ. Next, take the reading on the signal cable by measuring between the VC and EGLS pins and it should be somewhere between 0.1 kΩ and 5.5 kΩ, depending on the amount of vacuum applied.

Electronically Actuated EGR

With an electronically controlled EGR, check the output voltage by scanning the connector with the DMM on the rear and measuring the voltage. Be sure to leave the car in the ON position, but the engine should remain off. The measured values should be as follows:
• VC: 4.5 V to 5.5 V
• E2: 0 V
• ELGS: 0.3 V and 4.2 V (may vary depending on the valve position)

Reading Results

If the display on E2 is 5V, you will see the same display on EGLS, indicating that you have an open circuit.
If the measured value on VC and EGLS measures 5V, but 0V on E2, there could be an internal or external short circuit. In this case you should check the resistance between VC and EGLS. If it is less than 100Ω, there is a short circuit and the sensor must be replaced.
If the resistance is between 100Ω and 5,500Ω, there is a short circuit in the cables.
However, if the measured value shows 0V at E2 and 4.5V at EGLS, the sensor is damaged and must be replaced.

Recommended Tools to Fix P0405

Further Questions?

The P0405 code is most commonly caused by EGR (exhaust gas recirculation) problems and can be easily resolved. If you find anything confusing within the above article or have additional questions, just comment below and I will get back to you as soon as possible.

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Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.