Code P0404: Exhaust Gas Recirculation Circuit Range/Performance
For most makes and models of vehicles, a trouble code P0404 is the result of an improper reading from your exhaust gas recirculation valve. How do I fix trouble code P0404? Here are some common symptoms, causes and solutions that will help you restore your vehicle’s performance and remove this error code. The exact process is subject to the specifications of your vehicle, so always consult your service manual before attempting any repairs.
What Does Code P0404 Mean?
During normal operations, your vehicle uses an exhaust gas recirculation, or EGR, system to send exhaust gas back into your engine’s cylinders. This is used to lower the temperature of your cylinders and lowers oxides of nitrogen emissions.
The entire process is monitored and controlled carefully by a series of sensors, an electronically controlled EGR valve and your powertrain control module. Your powertrain control module receives signals to communicate whether your EGR valve is open or closed. A signal that doesn’t match the feedback circuit results in error code P0404.
Depending on the exact issue that caused your OBD-II scanner error code P0404 problem, there may be a range of symptoms or no symptoms at all. Your first sign will typically be your malfunction indicator lamp illuminating.
Depending on the position of your EGR valve, you may also notice a rough or absent idle. This is caused by a valve that’s stuck open. A valve that’s stuck closed will greatly increase your nitrogen oxide emission and the temperature of your cylinders. However, these open-valve symptoms won’t be obvious to you as you drive your vehicle.
Whether your valve is stuck open or closed, there are a few possible causes. A common cause is simply carbon buildup. During the normal operation of your EGR system, large amounts of carbon can easily build up around the EGR valve. Too much carbon can result in the valve sticking in the closed or open positions.
Another likely cause is a damaged EGR valve. Over time, this high-use valve can wear down. Either internal electrical issues or a bad seal can prevent it from functioning properly. Similarly, any issue with the wiring harness, ground circuit or even your powertrain control module could also cause error code P0404.
Because the most likely cause is a stuck EGR valve, your first step should be to inspect your valve using a scan tool. Use your service manual to find the location of your valve, and use your scan tool to command it to open and close. Be sure the valve moves correctly and the full range of movement isn’t blocked by any buildup.
If this doesn’t solve the issue, inspect the ground circuit. Most EGR valves operate on a five-volt circuit, so the reference wire should have a five-volt reading. Your ground wire should also show a good ground reading. As you command the EGR valve to open and close, you should see a change in voltage.
Any failure in the circuit could be caused by a single electrical issue. A broken, frayed, burnt or water-damaged wire could be the source of the error code. Pay particular attention to the connectors on your wire harness, as these can easily become dislodged, corroded or damaged.
Once you determine the source of the error code, you can confidently answer, what does the code P0404 mean? Once you resolve the issue, clear your code and test again to ensure there isn’t a secondary fault in the circuit. Look for similar codes in the 400 range, such as P0400, P0401, etc. These all point to particular issues with your EGR system and can help you identify the source of trouble code P0404.