P0406 Chrysler 300 – Diagnosis and Fixing the Problem

Chrysler 300 is a phenomenal car that has been gaining clout year after year since its introduction in 2005. This full-size sedan is powered by a range of engines, from the 2.7L V6 to the all-torquey 6.1L V8 version. When shopping for a full-size luxury sedan, many people worldwide pick the Chrysler 300.

P0406 code highlights

• Level of urgency:Medium
• Possible culprits:EGR valve problems
• Price for repair:$200 - $800
• If neglected:Bad efficiency, harsh work, loss of power
• DIY repairs:Impossible
• Can you drive?Carefully

P0406 Error code

P0406 is a code that comes about because the exhaust gas recirculation (EGR) has a high circuit voltage problem. The error code is generated when the ECM detects a higher than the standard voltage in the EGR. The check engine light (ECL) will then be illuminated to warn the driver of this EGR issue.

Many drivers of the Chrysler 300 have had to deal with the P0406 error code. This is an error code associated with the EGR system not working properly. This code will be seen in modern cars equipped with the exhaust gas recirculation system. The OBD II will help you diagnose an EGR issue early before any severe damage can happen.

We first need to understand the EGR system to understand what the P0406 error code means. We will examine how the EGR works and what issues it can encounter. These issues will make the EGR malfunction, thereby giving a P0406 error code. We take a closer look into the EGR system and what problems it can encounter to make it give error codes. We also look at ways of fixing any EGR issues and subsequently removing the P0406 error code.

Understanding the Exhaust Gas Recirculation (EGR)

EGR is found in every other modern car. It is an engine management system that recirculates exhaust gas to reduce carbon emissions. The system recirculates a specified amount of exhaust gas to the engine intake hence increasing the engine's efficiency. The EGR is also known to help reduce fuel consumption and lower harmful emissions such as nitrogen oxides, carbon monoxide, and hydrocarbons.

The introduction of the EGR in modern cars is more about obeying government regulations than improving the vehicle's comfort or efficiency. The EGR valve is exposed to extreme heat, corrosion, and contamination, which demands that it be made using tough materials.

The EGR valve, as it is commonly referred to, is designed to allow a precise quantity of exhaust gas to enter the engine through the intake system. This means there will be less oxygen in the combustion chamber, which makes the temperature to be lower by around 150^oC. Lesser oxygen also means a slower combustion process, which reduces the amount of harmful gaseous emissions from the engine.

The working of the EGR system is such that when your Chrysler is at idle or moving at low speeds, the EGR valve partially opens. This is because the engine requires less energy hence a small amount of oxygen. As the engine increases the amount of torque power to allow the car to accelerate or move up a hill, the EGR valve closes to allow more oxygen into the combustion chamber.

An EGR valve operates in a very harsh environment, resulting in wear and tear. However, the leading cause of EGR failing in many instances is the carbon particulates that accumulate along the intake system and the EGR valve passages. Over a prolonged period of driving your Chrysler 300, the tubes and the exhaust gas system can clog. Eventually, the EGR valve mechanism gets affected. The EGR may be forced to stay closed or open, leading to leakage via the valve diaphragm.

Why you should solve a P0406 code

The P0406 error code is categorized as a moderate fault that won't cause your vehicle to stall, at least immediately. However, if this error is ignored, there is a high risk that the catalytic converter and the whole emission system can become damaged.

The main reason why many of the Chrysler 300 drivers will find themselves in a fix as far as this error goes is that their vehicle cannot pass the smog inspection. Your Chrysler won't pass the smog test if it has a P0406 error code. To catch the problem early, you need to know the symptoms to look out for.

The P0406 symptoms in Chrysler 300

• Check engine light - In almost all cases, the CEL is the primary indicator of an EGR fault. It is, therefore, not wise to ignore this light on your dashboard.
• Engine stalling
• Lower fuel economy
• Production of harmful exhaust gases increases
• Combustion temperature increases
• Decreased engine performance
• Engine knock - Higher temperatures because of NOx may result in knocking sounds in the engine

What causes the P0406?

The P0406 code is caused by the EGR system not working as required. This code doesn't require you to look at the flex plate or the spark plugs but rather the EGR system. The cause of the error code can be anything, starting from a voltage issue or clogging of the system to a wiring issue. Here are the known causes of this error code;

• The EGR valve is dirty
• A wiring issue within the EGR circuit
• Shorted EGR sensor circuit
• A faulty EGR valve sensor

Diagnosing the P0406

The EGR valve for the Chrysler 300 is located under the hood. After reading a P0406 error code on the OBD II scanner, it is time to do several tests to know what the problem could be. The process, as stipulated in the service manual of the Chrysler 300, starts with you connecting the Engine Control Module (ECM) to the OBD II. This should be followed by turning the ignition key ON. Turn the EGR positioner to 100% before you can start scanning. Test the EGR transducer first to confirm that it is not the one with an issue.

Check the vacuum lines and all electrical connections to ensure they are correctly connected. While using a vacuum gauge, check the vacuum supply hose for the vacuum in the EGR valve, which should be anything between 2000 and 2500 RPM. Proceed and check the vacuum solenoid while the engine is running. If the vacuum solenoid is stuck, EGR's performance will be affected.

If the EGR works as expected, the valve stem moves accordingly. Such valve stem should be moving at a rate of between 1500 and 2000 RPM. If the valve stem is not moving and there is no vacuum, then there is an issue within the EGR system.

If the engine idles rough or stalls, it is time to check the entire EGR system to locate the root problem. There are instances where you will be required to remove the EGR valve to remove the carbon buildup, thus clearing the passages. While doing this, be careful not to contaminate the diaphragm.

To properly diagnose the P0406 code, you must also check the EGR sensor circuit. This is done by visually inspecting the system's wiring to confirm that it is not shorted or disconnected.

Fixing the P0406 code

It is imperative that you follow the service manual when diagnosing the EGR system of your Chrysler. As stated above, you risk damaging the diaphragm if you don't follow the laid-out instructions. It is also worth noting that it is possible to write of an EGR valve when all you were required to do was clean it or visually inspect it.

Any of the aforementioned reasons can cause the P0406 error code, and as such, you should ensure that you confirm that each of the EGR's components is working optimally. If, after clearing the error, the problem persists, then it is time you replace the EGR. The process involves;

Removing the engine cover and loosening the electrical cable on the EGR valve. You should then remove electrical connections and vacuum lines while checking for any signs of damage. Also, check for corrosion and carbon buildup.

Before fixing the new EGR valve, clean the mounting thoroughly. Ensure the valve, the gasket, and the bolt holes are lined up correctly. This should be followed up with tightening the fasteners and doing the torque settings procedure.

After everything has been done and confirmed, it is time to use the OBD II scanner to diagnose again. Scan Reset the ECM so that the check engine light is removed. Follow up with a road test to ensure the P0406 is eliminated for good.

Conclusion

The P0406 error in Chrysler 300 has been a nuisance for many drivers over the years. The good thing about this error is that it is easily diagnosed. Moreover, fixing the issue is easy if you have some engine knowledge and don't mind getting dirty. If you take the vehicle to the dealership, the labor cost will be around $200, if not less, while the price of a new EGR is about $100-300 depending on the brand.