Mazda Repair Questions? Ask Mechanics for Answers ASAP
The P0404 is a fairly straight forward code pointing to a problem with the EGR Solenoid. It's located under the hood, on the rear, passenger's side of the engine compartment (for an image location view, click here:https://www.dropbox.com/s/xjdeawmfrqp2vtz/egr-pos.jpg?dl=0 ). Very commonly, this is a vacuum line that has a crack, hole or disconnection, so carefully inspect the vacuum lines first. Inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the visual inspections check ok, replace the EGR Solenoid. If my answer has helped you, please help me by leaving a rating or accepting my answer so I may be credited. Rating or accepting my answer does not cost you extra. It allows me to be credited for my work. Please rate or accept. You can ask follow-up questions after you rate or accept.