P0404: Exhaust Gas Recirculation Circuit Range/Performance

What does the P0404 error code mean?

The diagnostic trouble code DTC P0404 indicates a fault in your car's exhaust gas recirculation (EGR) circuit range or performance. The code says that the car's engine control module has detected a problem with either the performance or the position feedback of the car's EGR valve. Specifically, this code indicates an issue with the control circuit for the EGR valve. The EGR system recirculates some of the exhaust gases produced by the engine into the intake system. Though it sounds counterintuitive, this bit of dirty exhaust air helps reduce nitrogen oxide emissions. 

Why is this issue important?

A faulty EGR system will significantly affect your engine's efficiency and emissions. Should the valve become stuck open or closed, it can cause increased exhaust emissions, poor performance, like a rough idle, and poor fuel economy. Increased emissions can also damage your catalytic converter and, if left untreated, lead to a failed emissions test.

Can I safely drive my car with this error code?

Driving with code P0404 is possible but not recommended. The vehicle may run poorly, and its fuel economy will likely decrease. Long-term driving with a malfunctioning EGR valve can lead to engine damage or other drivability issues. It's best to address the issue promptly to prevent further complications.

Common symptoms of the P0404 error code

• Illuminated check engine light
• Rough idling
• Engine hesitation or stalling
• Reduced fuel efficiency
• Increased exhaust emissions
• Knocking or pinging sounds during acceleration
  

How is the P0404 error code diagnosed?

1. OBD scan tool Inspection: Confirm the code and check for any related diagnostic trouble codes.
2. Visual examination: Inspect the EGR valve and wiring for obvious signs of damage or carbon buildup.
3. Live data analysis: Monitor the EGR valve position with a scan tool to see if it operates as commanded.
4. Valve function test: Use a vacuum pump or scan tool to actuate the EGR valve and check for proper response.
5. Electrical testing: Measure voltage and continuity in the EGR control circuit.
   

How is the P0404 error code repaired?

• Clean the EGR valve and passages to remove carbon buildup.
• Replace the EGR valve if it is faulty or sticking.
• Repair or replace damaged wiring or connectors in the EGR circuit.
• Update the engine control module software if a known issue exists.
• Clear the code and test the vehicle to ensure the issue is resolved.
  

Related reading

If you have other error codes you'd like to research, check out Edmunds' library of OBD-II Diagnostic Trouble Codes.