P0409 Exhaust Gas Recirculation Sensor Circuit “A”

OBD-II Trouble Code - P0409 - Data Sheet

P0409 - Exhaust Gas Recirculation Sensor "A" Circuit

What does trouble code P0409 mean?

This is a Generic Transmission Diagnostic Trouble Code (DTC), which means it applies to all makes / models from 1996 onwards. However, specific troubleshooting steps may differ from vehicle to vehicle.

An on-board diagnostic (OBD) trouble code P0409 is a generic trouble code associated with a problem in the exhaust gas recirculation (EGR) valve electrical circuit.

The exhaust gas recirculation valve is used to supply a controlled amount of exhaust gas to the intake manifold. The goal is to keep the cylinder head temperature below 2500 degrees Fahrenheit. Oxygen nitrates (Nox) are formed when temperatures rise above 2500 degrees Fahrenheit. Nox is responsible for smog and air pollution.

The control computer, either the powertrain control module (PCM), or the electronic control module (ECM) has detected an abnormally low, high, or nonexistent signal voltage.

How the exhaust gas recirculation works

DTC P0409 refers to the same problem on all vehicles, however there are many types of EGR, sensors and activation methods. The only similarity is that they all release exhaust gases into the intake manifold to cool the cylinder head.

Pouring exhaust gas into the engine at the wrong time lowers horsepower and causes it to idle or stall. With this in mind, computer programming only opens EGR at engine rpm above 2000 and closes under load.

Symptoms

P0409 has several typical symptoms. In all cases, the Check Engine indicator will be visible on the dashboard. The vehicle may experience lack of power and noise under heavy use. In some cases, no adverse symptoms are observed, except for the Check Engine indicator.

Symptoms depend on the position of the exhaust gas recirculation needle at the time of the fault.

• Soon the service engine light will come on and the OBD code P0409 will be set. Optionally, a second code may be set related to EGR sensor failure. P0405 refers to a low sensor voltage and P0406 refers to a high voltage situation.
• If the EGR pin is partially stuck open, the vehicle will not idle or stall.
• Knock ringing can be heard under load or at high rpm
• No symptoms

Possible Causes of Code P0409

• Exhaust gas recirculation sensor defective
• Defective wiring harness to the sensor
• The EGR pin is stuck in the closed position and carbon build-up is preventing it from opening
• Lack of vacuum at the exhaust gas recirculation solenoid.
• Faulty exhaust gas recirculation solenoid
• Exhaust gas recirculation position sensor defective
• The differential pressure feedback sensor of the exhaust gas recirculation system is defective.
• Faulty EGR valve
• Open or short circuit in wiring harness
• Carbon deposits on the EGR valve
• Faulty EGR solenoid or position sensor

Repair procedures

All EGR valves have one thing in common - they recirculate exhaust gases from the exhaust system to the intake manifold. In addition, they differ in the methods of regulating the opening of the needle and determining its position.

The following repair procedures are the most common problems that account for most EGR failures. If the wiring harness or sensor fails, a service manual is required to determine the correct wire identification and diagnostic procedures.

Be aware that wiring varies from manufacturer to manufacturer, and computers do not respond well if the wrong wire is probed. If you examine the wrong wire and send excessive voltage across the computer's sensor input terminal, the computer will start to burn.

At the same time, if the wrong connector is disconnected, the computer may lose programming, making it impossible to start the engine until the dealer reprograms the computer.

• P0409 indicates a circuit malfunction, so check the EGR sensor connector for corrosion, bent or extruded terminals, or a loose connection. Remove the rust and reinstall the connector.
• Disconnect the electrical connector and remove the exhaust gas recirculation system. Check the exhaust gas recirculation inlet and outlet for coke. If necessary, clean of coke so that the needle moves smoothly up and down.
• Check the vacuum line from the exhaust gas recirculation system to the solenoid and replace it if any defects are found.
• Check the solenoid electrical connector for corrosion or defects.
• If the vehicle is a Ford, follow the two vacuum hoses from the exhaust gas recirculation system to the differential pressure feedback exhaust gas recirculation (DPFE) sensor at the rear of the manifold.
• Check the two pressure hoses for corrosion. Experience has shown that these hoses drown out carbon deposits from the exhaust pipe. Use a small pocket screwdriver or similar to remove any corrosion from the hoses and the sensor will start working again.

If the most common tests do not solve the problem, a service manual is needed to continue checking the electrical circuits. The best solution is to take the car to a service center with the appropriate diagnostic equipment. They can quickly identify and fix this type of problem.

Associated EGR Codes: P0400, P0401, P0402, P0403, P0404, P0405, P0406, P0407, P0408

Common Mistakes When Diagnosing Code P0409

Errors are visible when steps are overlooked or not performed in the proper order. This can lead to the fact that the replacement of serviceable parts will be a waste of time and money.

How serious is the P0409 code?

P0409 can be a minor annoyance, but should not prevent the vehicle from moving to safety after the code is seen. The EGR system is used to recirculate exhaust gases back into the intake to help with emissions and prevent OBD2 emissions from passing while code P0409 is present.

What repairs can fix code P0409?

• Replacing the EGR valve
• EGR valve decoking
• Repair or replacement of wiring harness
• EGR solenoid replacement
• Replacing the EGR position sensor

Additional comments to consider regarding code P0409

In cases where the EGR valve is stuck open or closed due to soot, it can be removed with cleaning products, which in some cases will solve the problem. Purifier throttle body can be used to remove carbon deposits and restore the operation of the exhaust gas recirculation valve.

How to Fix P0409 Engine Code in 3 Minutes [2 DIY Methods / Only $4.76]

Need more help with your p0409 code?

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NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.