P0404 Code – Meaning, Causes, Symptoms (& How To Fix)

You’ve just seen the Check Engine Light come on and you are stumped as to what could be causing the problem. The P0404 code might be displayed by your OBD-II scanner. But what is this?

We explain what the P0404 DTC is and how to fix it. You will also find the most common symptoms and some tips on how to treat it. The EGR system may even be better understood by the time you are done. 

Definition of code P0404

P0404 – Exhaust Gas Recirculation “A” Circuit Range/Performance

What does the P0404 code mean?

P0404 is a diagnostic code that indicates an Exhaust Gas Recycling Circuit Range/Performance problem. This generic trouble code comes from the powertrain control module (PCM), showing that the Exhaust Gas Recirculation (EGR) valve operation isn’t accurate.

Normally, this code indicates that the parameters aren’t in line with where they should be with the EGR valve. This code is used to indicate that the EGR valve's parameters are not in line. 

P0404 Trouble code Symptoms

The Check Engine Light will only come on in most cases if the P0404 trouble code has been entered. Other than that, there might not be any issues with performance. There may be additional symptoms in rare instances.

These are some of the most frequent P0404 symptoms.

The P0404 Code: Causes

The only way to figure out what’s causing the P0404 trouble code is to walk through our complete diagnostic steps listed below. You might discover that one or more of the following causes are to blame after your exam.

• Defective EGR valve/sensor
• EGR pipe or valve clogged
• Ground or electrical short circuit
• Malfunctioning PCM
• Leakage in intake
• Faulty MAF/MAP sensor

RELATED: 6 Symptoms of a Bad EGR Valve (& Replacement Cost)

What is the P0404 code?

Medium – Because the Check Engine Light might be the only problem you notice, you might think it’s safe to drive wherever you want and procrastinate on a fix. It's a terrible idea.

It is important to get the problem fixed as soon as possible. Continue driving with this problem can lead to more serious engine problems that could increase repair costs. 

How can you fix the P0404 code?

You don’t need to wonder what’s going to fix the P0404 DTC. Do a thorough diagnostic examination to find out the cause. Once you know what’s causing the problem, you can get it fixed.

Below are some common solutions to P0404.

• Ground or circuit short repair
• Make sure to clean the EGR Valve and pipes
• Replacing the EGR sensor/valve
• Replace/update PCM
• Fix the intake leak
• Replace MAF/MAP sensor

RELATED: 3 Signs of a Bad EGR Temperature Sensor (& Replacement Cost)

Common errors in P0404 diagnosis

You don't want to have to change the EGR valve, sensor, or other component without thoroughly inspecting it. You might spend money to replace a part when it’s not needed.

You could have a problem with a loose connection or frayed wire. It is better to fix the wiring issue than replace the part. 

How do you diagnose the P0404 trouble code?

If you’ve never worked with the EGR system, you might not know how to diagnose a problem. We have the same steps that a professional mechanic would use, making it easier to figure out what’s wrong.

Here are some steps to follow, as long as they fall in line with your car’s service manual.

1. All trouble codes should be read. Use freeze frame data to pinpoint what’s going on. 
2. Make sure to inspect all connections. Check for loose connections or frayed wires.
3. For carbon buildup, inspect the EGR Valve. Clean the carbon off and check if it fixes the problem. 
4. Verify the values of the MAF or MAP sensors. If the sensor is dirty or worn out, clean it and replace it as soon as possible.
5. Intake leaks and leaks in the EGR pipes should be checked.
6. Based on your findings, replace the EGR sensor/valve. 

If these steps don’t help you figure out what’s going on, it’s best to visit a professional mechanic. You can find the right equipment at your auto shop to help you diagnose the problem. Without too much trouble, they can reprogram the or replace your PCM. 

Repair cost estimate P0404

You can expect a different repair cost depending on the nature of your problem. The repair cost we have provided below is an estimate of labor and part costs. You might save money if you are able to do the repairs yourself. 

• Repair electrical short in circuit or ground – $50-$500
• Replace EGR valve/sensor – $250-$650
• Update/replace PCM – $250-$2,500
• Replace MAF/MAP sensor – $200 – $500

Here are some mechanics tips about the P0404 code

You must understand your EGR system before you are able to repair the P0404 DTC. Your car’s EGR system is responsible for redirecting exhaust gas through the engine so the cylinder temperatures can be reduced. For a cleaner environment, this process reduces nitrogen oxide emission. 

In the EGR system, there’s a valve needed to regulate the amount of flow of exhaust that’s moving back into the motor. This valve can be controlled via the PCM. The sensor also sends information back to the PCM, showing the valve's position.

You will be able to understand the EGR system and what is in the manual. This knowledge will allow you to fix the problem yourself after an extensive diagnostic. For more information about EGR, you can visit the EGR website. To get further assistance, you will need to go to a professional shop.

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