The Electronic Throttle Control(ETC) system's components are the 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.
PCM sets DTC P0638 if the PCM detects TPS adaptation value exceeds threshold value.
Item
Detecting Condition
Possible Cause
DTC
Strategy
Case1
TPS adaptation condition check
Poor connection or damaged harness
Faulty ETC Motor
Faulty TPS
Case2
ETC Limp Home position check
Case3
Lower mechanical stop adaptation voltage range check
Enable Conditions
During TPS adaptation
Threshold
Value
TPS adaptation is requested but not possible
Difference between Throttle sensor voltage in limphome and limphome setpoint > 0.3V
Difference between Throttle sensor voltage in lower mechanical stop position and lower mechanical stop position setpoint > 0.3V
Diagnostic Time
1.2 sec.
Limp-Home
Forced limited RPM mode : The PCM limits engine speed to 1500rpm
Electrical check of the ETC system is prohibited
MIL On Condition
Immediate