The error code P0404 in a Buick Regal indicates that the Engine Gas recirculation (EGR) valve or sensor is out of range or that its performance is out of parameters. This is an OBD-II generic code. This function is critical to the vehicle’s operation. The EGR redirects exhaust gas into the cylinders, when the EGR is too high the vehicle will not idle and therefore will stall.
This is caused by a build-up of carbon form gas emissions. This can also cause issues with the engine coolant. In comparison, the P1404 code refers to an error with the Engine Gas recirculation sensor’s wiring.
Symptoms
- The check engine light is illuminated on the vehicles’ dashboard. This light appears when the sensor or valve is out of position by at least fifteen percent. It is most likely that the vehicle’s engine operates electronically and not with a vacuum system, which means an electronic diagnostic can be run to determine by what percent the system may be off.
- There may be pre-ignition on the acceleration.
- The engine may run rough, hesitate, or stall. The increased carbon emissions cause the vehicle to be unable to idle.
Causes of the P0404 error
- The EGR sensor may be moved out of position. This can be caused by a build up of carbon around the valve or just use over time.
- The EGR valve has a jerky movement when opening and closing. The valve needs to be able to open and close smoothly.
- The EGR sensor went above its gas emission limits.
- There may be damaged or shorted wires connected to the EGR valve. This would only apply to electronic systems and not to a valve that operates with a vacuum system.
Solutions
- You can remove any carbon build up that may prevent the EGR valve from opening and closing correctly.
- You can use a scan tool to open and close the EGR valve to determine if the valve or sensor is out of position.
- You may try repositioning the EGR sensor. After a diagnostic, you should be able to determine by what percentage the sensor is out of place.
- You may repair or replace any damaged EGR sensor wires. This would refer to the circuit wires which should have a five volt feedback to the circuit board. You can test this on the vehicle’s circuit board.
- You may need to replace the EGR valve. Follow this link to purchase one from Amazon.
The P0404 error code typically appears in the Buick Regal because of a carbon build up around the EGR valve that prevents the valve from closing properly. This is a critical engine function and should be addressed right away to prevent any serious engine damage caused by gas emission. These are a few simple steps that you can try at home to remedy this issue once the cause has been determined.
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