One problem related to engine exhaust system has been reported for the 2003 Hyundai Sonata. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Hyundai Sonata based on all problems reported for the 2003 Sonata.
2003 Hyundai Sonata egr issues (check engine light 401)- I've been having persistent issues with my vehicle's egr system for over a year now. I have replaced the entire egr system including the egr valve, solenoid, etc. I have also had to replace other parts that have failed due to the malfunctioning egr - ignition coils, spark plugs. Even after replacing all these parts, my vehicle still complains about the egr with check engine light constantly on (401). I have also been getting very poor mileage. I contacted Hyundai about a TSB they sent out to dealers for egr diagnosis. Hyundai denied assistance with this issue and asked me to contact the dealership directly. The dealer wants to charge me a diagnostic fee to look into the issue + fees for parts. Searching on the internet, I found several cases of egr malfunctioning with 2003 models. Hyundai needs to look into this.