P0404Hyundai SonataYears: 1996 - 2026
EGR Circuit Range/Performance
Reviewed by ASE Certified Technician
What does this mean?
Code P0404 indicates a problem with the Exhaust Gas Recirculation (EGR) system. The EGR system reduces NOx emissions by recirculating a portion of exhaust gas into the intake manifold.
Disclaimer: This diagnostic code is part of the standard OBD2 system and can apply to Hyundai Sonata models manufactured from 1996 to 2026. However, please note that the presence of this specific code depends on your vehicle's exact engine configuration, options, and production year.
Advertisement (In-Article)
Common Causes
Stuck or faulty EGR valve
Clogged EGR passages
Damaged, chafed, or broken wiring harness
Vacuum leak in intake system
Corroded or loose electrical connector
Symptoms to Watch For
- Check Engine Light is illuminated
- Rough or unstable idle
- Engine knocking or detonation noise
- Failed emissions test
- Engine stalling or dying unexpectedly
- Significant loss of engine power