The Electronic Throttle Control(ETC) system is made of the components throttle body, Throttle Position Sensor(TPS)1&2 and Accelerator Position Sensor(APS) 1&2. The throttle body contains the actuator, the throttle plate and the throttle position sensor (potentiometer), which are integrated in one housing. The actuator consists of a DC motor with a two-stage gear. The opening angle of the throttle valve is detected by the throttle position sensor which is mounted on the throttle body. And it provides feedback to the PCM to control the throttle motor in order to control the throttle valve opening angle properly in response to the driving condition.
Checking output signals from TPS under detecting condition, if the difference between real and target throttle position is above the specified value, PCM sets P0638.
Item
Detecting Condition
Possible cause
DTC Strategy
Limp-home check
Throttle stuck
Open in motor circuit
Faulty motor
Faulty PCM
Enable Conditions
Ig On
Threshold value
Limp-home position > 13.1% or < 1.8%
Diagnosis Time
-
MIL On Condition
2 driving cycle
Fig.1) Normal waveform of ETC motor & TPS1 at idle.
Fig.2) Normal waveform of ETC motor & TPS1 with deceleration