Headlights burning out frequently was the first sign of problems, replaced them as the dealer said this was inherent to the 2001 Elantra. In August 2006 check engine light came on. Also, the air bag sensor light was on, headlight out again, took car to dealer, they called back and said that the alternator had been over charging and not only was the over charging burning out the headlights it also had taken out the cruise control module, and air bag module. Car had only 42000 miles on it, and was 2 weeks from being out of the 5 year bumper to bumper warranty. Well here it is 6 months later and 47000 miles and check engine light is back on, I have since purchased a diagnostic tool to read the codes. The car was running rough at idle. The codes came up as mis fire on cylinder 3, tps sensor failure and map barometer failure. I replaced the plugs and wires, engine still ran rough. Took car back to dealer they replaced the tps, still running rough, they suggested that because of the faulty tps that the excessive dumping of fuel into the jets could have caused one of them to be clogged. I had them clean the jets as well as replace the plugs and wires again (they had also found that #3 wire had been arcing.) this took care of the idle problem. I took the car home and the next day driving the car would surge between 3rd and 4th gear, engine light back on. Still have the map error. Dealer ended up replacing the map sensor. It has been about a month since this last occourence and all I can do is cross my fingers until I trade it in. Abl.pco

- Taylorsville, UT, USA