P0403 Engine code is the bane of my existence. I have been fighting with this code for 2 years now in my wife's 2004 Tribute V6.

The code is egr circuit malfunction. Ive replaced the EGR valve and solenoid with brand new parts. Ive had it to the mechanic and he cant figure it out either. He keeps telling the only parts to really fail in this system are the 2 i already replaced. I live in NJ and the DMV inspection has been past due for 9 months now because i cannot figure whats actually wrong. I am a hand on guy with a mechanical mind and can swap out parts no problem, but i dont know enough about engines and the way exhaust is handled to really diagnose this problem.

The car runs great, but wont pass inspection with this code on. Anybody else have a similar problem or know what else i could try?

thanks!

 

i have the same problem. p0403 egr valve circuit malfunction. its the same thing on my 2008 mazda 3 hatchback 2.3 L. ive been battling this for a year now. i have done just about everything except replace wire harness or reprogram. today i took off the intake manifold (took me 2 days) and i cleaned out everything and replaced all vacuum hoses. car has @144k on it and i dont drive it much at all. im a daily motorcyclist. so i have to schedule an appointment once every blue moon to at least drive it around the block or run it on the hwy. i keep very little gas in it.
i replaced egr 4 times so its not that. im pretty good with the labor, just cant figure this one out. too bad this egr isnt all mechanical. all vacuum and mechanical normally works more often than these modern ones. ive ran car several times over 200 miles after couple of egr replacements and still cant shake the p0403. i need to wire the damn solenoid directly to the battery if i get to that point. this ridiculous. definitely not like my motorcycle. its probably a ground on the pcm. i checked the resistance on the egr side and the harness side. just when i tried to test the pcm/ecu computer i coulnd find anything small enough to poke in the wire connector. its too tiny. does anyone have any ideas on what to use to probe into that computer harness right next to the battery? i need to check for short or open circuit or i need to ground it out somewhere. From egr solenoid to pcm/ecu or whatever it is called. Ground has been the culprit alot in my experience. i have a zurich scanner tool and obdII plug device. Not too fluent on the using of these but im learning as i go. no recalls on my mazda 3. dont know what program i can use to change settings or re-install software. i also got another computer for my car but dont have the keys to that. do people sell wiring harnesses on this mazda site? oh the 2 wires going to my purge valve does it matter which wire is which? i had replaced the wire on my purge and dont recall which one connected out of the two. Polarity is the question. thanks gary r. in Saginaw texas

 

same issue with my 2008 mazda3 hatchback 2.3ltr. p0403 egr open circuit problem going on for nearly 2 years now. i have done everything. i am a mechanic. i even made my own wire harness direct to pcm . both connections passed ohms and resistance. after 4 different egr's i installed oem mazda egr and it worked. the list is long from everything i done prior...with taking off the intake manifold, replaced all vaccum on manifold, to pcv valves, harness pigtails, continuity checks.... it was borderline nightmare. even reset intake throttle. new backup onboard computer pcm, (for troubleshooting) scan tools zurich, tuneups, salvage yard trips, obd2 plug in device, etc. list dont end.... im a daily motorcyclist and this car is for rainy days or had a too close of call the day before on motorcycle back up car.... after multiple pcm relearns at 144k post repair...i did the oem. so seems like a what hp tries to do with the printer chips. keeping it original co. for profit and aftermarket cant step in and take business away. comes down to $$. these things are designed to fail before long. thats what keeps economy going. if i was the engineer and car designer my stuff would not break down as often. and all my cars front hood would open like a semi 18 wheeler. screw the aerodynamics and tight fit of engine. my stuff you can get to everything easily. as easily as if engine was on an engine stand. its ridiculous how you can never get to anything easily. is a comical game of who can get to what and look at the frustration. the engineers who design these cars dont even work on em. thats why they are the way they are. smh smh