Air in hyundai comes on by its self - 2008 Hyundai Elantra

Fuel injection is self bleeding, so that is not the problem, it is my guess you burned out the in fuel tank fuel pump. The tiny pump depends on the cool gas to lubricate and cool itself, so running out of gas can very quickly destroy the fuel pump.

Probably Engine Management System has recognized a fault or a part operating out of tolerance. Sometimes will self-rectify!
top things to check:

• O2 sensor (part of the emissions system, monitoring and helping adjust the air-fuel mixture)
• Loose gas cap
• Catalytic converter
• Mass air flow sensor (monitoring the amount of air mixed in the fuel injection system)
• Spark plug wires

this refers to the fuel being to lean, there may be a leak in a air intake pipe or the air filter has become dislodged , check also for a fuel leak , check for a worn vacuum pipr , get your self a workshop manual will give you step by step guide's, also try a fuel addative , get one that covers the catalytic convertor as well as the valves etc keep me posted if you wish

Air bag lights self reset you still have a existing problem during the self test it has detected a open/shorted circuit disabling the system. watch your air bag light then turn key on do not start engine lamp comes on then goes out and then comes back on again. this is the start up initialization of the system and sensor or wiring does not pass the system goes fail safe. with a scanner the air bag code can be read thru the OBDii connector if having hyundai body control software.

P1124 - Throttle Position Sensor Out Of Self Test Range
P1124 = Long Term Fuel Trim Additive, Air System too lean

Shoulda gone to HMAservice.com. It's free and has the correct codes for your Hyundai.

Good luck.

It might have something to do with your mass/air sensor located on the intake tube. Try cleaning the mass air sensor with the appropriate cleaner and also try cleaning the throttle body with carb cleaner.

P1402
Power Stage (DMTL Motor)

P1403
Power Stage (DMTL Valve)

The 2000 model year Accent adopts a new "pressurized" leak check system capable of detecting a 0.020" (0.5 mm) diameter leak (previous Hyundai systems detect a 0.040" [1mm] diameter leak using engine vacuum). The new system uses a Diagnostic Module for Tank Leakage (DM-TL) to close and pressurize the fuel evaporative emissions system. The DM-TL replaces the fuel tank pressure sensor and the canister close valve from previous systems. Other significant changes were made to the system logic, including several new diagnostic trouble codes. The diagnostic module (refer to photos on page 3) consists of a motorized air pump, a solenoid shuttle (sealing) valve, and a 0.020" (0.5 mm) diameter reference orifice. After the vehicle meets the self check requirements (see Self Check Requirements When Not Using The Hi-Scan Pro Section), the DM-TL activates to check for system leakage. The air pump and shuttle valve work on the command of the ECM. Motorized Air Pump - the pump pressurizes the evaporative emissions system producing a current draw that the ECM reads to determine pass/fail conditions. When the pump is switched 'ON', current draw is typically 17 - 36 mA. Solenoid Shuttle Valve - the shuttle (sealing) valve has two sealing sides (front and rear) that provide two functions: A. When the valve is "OFF" (no voltage aplied to valve), the front sealing surface directs air from the air pump (if it is "ON") through the 0.020" (0.5mm) diameter reference orifice. The rear sealing surface is openand provides an open path between the charcoal canister and freshair. B. When the valve is "ON" the front sealing surface is open directing air from the air pump into the evaporative emissions system. The rear sealing surface is closed, sealing off the evaporative emission system for the leak check. 0.020" (0.5 mm) Diameter Reference Orifice - the built-in reference orifice provides the ECM the current draw of the air pump motor for current ambient conditions (temperature,humidity etc.) to determine pass/fail conditions duringthe system leak check. P1402 DM-TL Circuit Continuity Check (Pump Motor) - short circuited, or disconnected. P1403 DM-TL Circuit Continuity Check (Shuttle Valve) - short circuited, or disconnected. IMPORTANT NOTE!.. you have a fuel leak now. These codes are NOT a direct cause of that leak... they are a result.



It is highly recommended to use the Hyundai Hi-Scan Pro to activate the evaporative emission self check. Using theHi-Scan Pro will save time and provide more consistent results. Moreover, "road testing" of the evaporative emission system in a 2000 MY Accent is not practical (requiring up to a 4day time frame to verify a repair). The leakage self check can be found on the main menu after selecting Model and Year of the vehicle. For the 2000 Accent, the menu item is labeled "DM-TL Test". To familarize yourself with the operation of the self check, remove the fuel cap of a 2000 Accent that is operating properly and activate the self check (follow the instructions on the Hi-ScanPro screen). With the fuel cap removed, Diagnostic Trouble CodeP0455, or P0442 will register in the ECM memory after the test is finished. (NOTE: The "Check Engine" light will not illuminate because the self check has only been run once. However, the code will be stored in the ECM memory. The "Check Engine" light will illuminate if the ignition key is switched to off, and the main power relay shuts off, and then the self check is performeda second time.). Erase the code when finished, and securely replace the fuel cap. If no code appears, turn the ignition key to off until the main power relay shuts off and retry the process. If no code appears at this point, call the Hyundai Tech Line. 7. SYSTEM SELF CHECK REQUIREMENTS (WHEN NOT ACTIVATED BY HI-SCAN PRO) For verification of a repair, it is highly recommended to use the Hi-Scan Pro to activate the self check. The importance of using the Hi-Scan Pro can't be over-emphasized because of the different self check requirements for the 2000 Accent. Use of the Hi-Scan Pro bypasses all of the self check criteria described below, allowing the technician to perform the self check at anytime, regardless of the conditions. Under normal operating conditions, the leak check occurs almost immediately after the vehicle is shut off and items 1-8 have been achieved. The ECM"s prerequisite for this check areas follows:

1. Vehicle must have cooled down (not driven) a minimum of 5 hours (typically overnight).
2. Vehicle must have been driven 20 minutes or more.
3. Engine "off" and ignition key "off".
4. Vehicle"s fuel level must be between 15% - 85% full.
5. Ambient temperature between 39ðF - 95ðF (4ð - 35ðC).
6. Altitude lower than 8250 feet (2500 m).
7. Battery Voltage between 11.5 - 14.5 volts.
8. Activates every other time (every second time) after conditions 1-7 are met.

NOTE The leak check will occur regardless of fuel level when conditions 1-7 are met, if the ECM has stored a DTC for the fuellevel sensor (P0460; Fuel Level Sensor Rationality Check).

Almost every car(including yours) has a flow through ventilation system which means even with the air turned off air will still come through the vents. Its hot because of outside temp and engine temp. 
Basically just push the recirculation button and it will stop.

so, is it a switch on the knob? Mine started acting up today.