Hyundai Sonata LF: Engine Control System / Accelerator Position Sensor (APS) Description and Operation
Accelerator Position Sensor (APS) is installed on the
accelerator pedal module and detects the rotation angle of the
accelerator pedal. The APS is one of the most important sensors in
engine control system, so it consists of the two sensors which adapt
individual sensor power and ground line. The second sensor monitors the
first sensor and its output voltage is half of the first one. If the
ratio of the sensor 1 and 2 is out of the range (approximately 1/2), the
diagnostic system judges that it is abnormal.

Inspection
1.
Connect the GDS on the Data Link Connector (DLC).
2.
Measure the output voltage of the RPS at idle and various engine speed.
ConditionOutput Voltage (V)Idle Approx...
Other information:
Replacement And Air Bleeding
Never remove the radiator cap when the engine is hot. Serious
scalding could be caused by hot fluid under high pressure escaping from
the radiator.
When pouring engine coolant, be sure to shut the relay box
lid and not to let coolant spill on the electrical parts or the paint...
S..