P0404 code definition
Exhaust Gas Recirculation Circuit Range/Performance
What the P0404 code means
P0404 is an OBD-II generic code that the engine control module (ECM) detected the engine exhaust gas recirculation (EGR) valve or sensor is out of specification range or its performance has gone out of specification parameters.
What causes the P0404 code?
The ECM monitors the EGR position with a sensor mounted on top of the EGR valve and the valve was out of a set position when the EGR was commanded closed.
The EGR valve movement should be smooth without jerking or the ECM sets the code.
The EGR sensor went above upper limits when the EGR was commanded open by the ECM.
What are the symptoms of the P0404 code?
- The Check Engine Light will be illuminated and the code is set in ECM memory.
- The engine may have pre-ignition on acceleration.
- The engine EGR system can cause the engine to run rough, hesitate or even stall if it is not indicating the proper EGR valve position to the ECM.
How does a mechanic diagnose the P0404 code?
Scans codes and documents the freeze frame data in order to verify the problem
Clears the engine codes and road tests to verify if the concern comes back
Monitors the EGR sensor pid on a scanner to see if sensor indicates the valve is stuck open or not moving smoothly
Removes the EGR sensor and manually operate the sensor to isolate a valve or sensor failure
Removes and checks the EGR valve to verify it is not carboned up, causing the bad sensor readings.
Common mistakes when diagnosing the P0404 code
Not operating the EGR position sensor manually to isolate a valve or sensor failure before replacing components
Not checking the wiring harness and connection to the EGR position sensor for problems before replacing the EGR position sensor or EGR valve
How serious is the P0404 code?
An EGR system that triggers this code the ECM may disable the EGR system and render it inoperative.
The Check Engine Light being on causes the vehicle to fail emission testing.
The EGR position is critical for the ECM to properly control EGR valve opening and closing.
What repairs can fix the P0404 code?
Replacing the EGR valve if it stuck partly open from carbon buildup in the pintle area and cannot be cleaned.
Replacing the EGR position sensor if it is determined that it cannot give a correct input reading to the ECM when moved manually
Repairing the wiring that is shorted or open to the EGR position sensor or connector
Additional comments for consideration regarding the P0404 code
Code P0404 is triggered when the EGR position is not as the ECM expected and the most common cause is the EGR valve partly stuck open from carbon buildup on the valve pintle.
Need help with a P0404 code?
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