P0404 Code: Meaning, Symptoms, Causes, Diagnostics, and Fixes

The exhaust gas recirculation system in your car helps to reduce smog emissions. It’s also crucial to maintaining the correct engine temperature and air-to-fuel ratio. When the P0404 code activates, one of the components of this system is not functioning the way it should.

While the EGR valve is the main component in this system, it’s not always the cause of P0404 problems. Many times, the wiring, sensor, or other electronic components are to blame. This makes a thorough diagnosis especially important in getting to the root of the issue. 

If your vehicle is giving you a P0404 trouble code, there are a few easy steps you can follow to diagnose it. Read on below to learn what this code means, and what to do about it.

P0404 Code Definition

P0404 Code Definition (Generic): Exhaust Gas Recirculation “A” Circuit Range/Performance

P0404 Chrysler Code Definition: EGR Control Circuit Range

P0404 Dodge Code definition: EGR Position Sensor Signal Performance

What Does P0404 Mean?

The primary function of your exhaust gas recirculation (EGR) system is to redirect the exhaust fumes back into the engine. This lowers the temperature of the cylinders, reducing harmful smog emissions. 

Depending on how your engine is running, your valve will be opened or closed to increase or decrease the flow of exhaust gas. The power control module (PCM) interacts with the feedback system on the EGR valve. It tracks when it’s fully open, fully closed, or partially open.

OBD2 scan tool is the best way to diagnose the error P0404 code
To diagnose the P0404 code, using an OBD2 scanner is the best choice.

If the EGR valve is behaving in a way it shouldn’t, the P0404 trouble code is triggered. Usually, this means the valve is not opening when it should, but it can also get stuck open, or be misbehaving in other ways.

While P0404 is a generic powertrain code, the fix can be different depending on your vehicle’s make and model. It’s most likely to appear in systems with an electronic EGR valve, as opposed to a vacuum-controlled valve. 

What Are The Symptoms of The P0404 Code?

You may not experience any drivability issues with the P0404 trouble code. If there are symptoms, they will differ depending on whether the valve is stuck open or closed. General symptoms of P0404 include:

Symptoms of an open EGR valve include:

  • Rough idle
  • Engine hesitates and stalls when idling

If the EGR valve is stuck closed, you won’t experience these drivability issues, but you may notice an increase in the engine combustion temperature and smog emission levels.

What are the Causes of P0404?

  • Failed or faulty EGR valve
  • Carbon build-up on EGR valve
  • Failed or faulty EGR sensor
  • Faulty or damaged wiring or connections in the EGR system
  • Short or open circuits (reference circuit, ground circuit, etc.)
  • Faulty PCM (rare)

How Serious Is The P0404 Code?

The P0404 code is somewhat serious. You could go a while with a P0404 code active and not notice any changes in how your car drives. However, your vehicle will produce more smog. A faulty EGR valve can lead to long-term engine damage, as well. While you can drive safely in the short-term with this code active, you should address it as soon as possible.

How To Diagnose And Fix The P0404 Code

Tools you’ll need:

  1. Scan your system with the OBD2 scan tool. You may see other related codes, including P0400-P0409. These can help you identify which part of the EGR system is causing the issue. 
  2. Check the freeze frame data using your OBD2 scan tool. Evaluate the conditions under which the code was set, then clear the codes and test drive your car, replicating those conditions as closely as possible. Pieces of carbon may become temporarily lodged in the valve, creating intermittent problems that fix themselves when the blockage clears. If the code returns, continue with the repair. 
  3. In some cases, P0404 is an issue with the EGR sensor rather than the valve itself. You can use the combustion data from your engine to determine whether this is the case.
  4. Use your scan tool to open the EGR valve. Watch the physical valve as you do this. Compare the valve’s actual position with the desired position on your scan tool. If they match, the valve is functioning correctly. 
  5. Examine the wires around the EGR system for signs of corrosion or damage. Check the connections, too, to make sure no wires are loose, and that none of the connectors are damaged. Replace, reconnect, or tighten as necessary.
  6. Visually examine the EGR valve for signs of carbon build-up. If you see any, remove the valve and clean it with carburetor cleaner. Reinstall the valve, then clear codes and test drive your vehicle. 
  7. If the code returns, test the EGR ground circuit using a digital multimeter. If it doesn’t indicate a good ground, replace it. Also, check the reference voltage of the connector. It should show a 5-volt reference circuit. If it doesn’t, replace it.
  8. Check the control circuit with a digital multimeter. The voltage should vary as the EGR valve changes positions. If it doesn’t, there’s an open or short that needs to be addressed.
  9. If the EGR valve seems to be functioning properly and there are no issues with the circuits or grounds, replace the EGR sensor. 
  10. Should the code still not clear, you may have a more serious electrical issue. While this is a rare cause of the P0404 trouble code, you should take your vehicle to a mechanic for further diagnosis.

Common Mistakes To Avoid While Diagnosing The P0404 Code

Many people replace the EGR valve or EGR sensor before they check the wiring and connections. Don’t overlook the smaller potential causes. Not only are they easier to fix, but failing to address them will mean your system continues to have problems. 

Tips To Avoid P0404 In The Future

Loose and damaged wires in the EGR system are common causes of the P0404 code. Be sure you fully tighten all connections when installing components. You can also check the wiring as part of your regular maintenance routine.

How To Fix P0404 EGR Code

Read more: OBD2 Codes: Full List Meaning & Fix Guide

Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Diagnostic Tools and Auto Repair". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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