My car seems to be chugging when idling or randomly driving somewhere. Checked all my fluids and they seem to be fine. My check engine light was on for a while the trouble shooting code was p1154. code summary was o2 transition time malfunction bank 2 sensor 1. The engine light came off recently! My heater was making loud noise before it stopped working and when switch to on it made my car run unusual. I don't know if that has anything to do with my car but figured i'd add it in since it was causing some of an issue when it worked.

SOURCE: Hyundai 2001 Accent Code - P0130

I think this is the O2 sensor - It will run fine but you might notice your gas mileage slipping and will not pass emissions.

SOURCE: 2002 Hyundai Sonata wont pass smog

CA you can take the car to a referree and get a one time waiver if you have spent a minimum of $450 on repairs not including smog fees. Gives you two years to get it fixed. Smog Referee Call Center
Toll Free: 1.800.622.7733
You can also sell the car to the state for "up to" $1,000

SOURCE: 2001 Elantra stall, loss of power. Driving at

I am having the exact same problem with my 2001 Hyundai Elantra. I was told that the engine code that comes up when the sensor is on is called "Absolute Pressure In The Manifold". I was told by a "Hyundai Specialist" that when that code comes up it usually means that the seal on the manifold is Fuct. When my mechanic checked that out for me he had noticed that my manifold had 4 cracks in it(can varify cause he showed me). He replaced the manifold and gasket. The car ran fine for about 2-3 days and since then the problem has since come back and my check engine light will no longer go on/off it only stays on. Because of the check engine light always staying on I have noticed that on many occasions my car will hiccup many times in a row. The only way to stop the hiccup I have noticed is to take my foot right of the gas for approx. 2-3 sec then car will continue without hiccup(till it happends all over again). All in all I have been having this problem now for approx. 1 year and if there is somehow someway it could be repaired I would appretiate it.