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 ECM to control the throttle motor in order to control the throttle valve opening angle properly in response to the driving condition.
ECM sets DTC P0638 if the ECM 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 ECM limits engine speed to 1500rpm
? Electrical check of the ETC system is prohibited
Test Condition
TPS1
TPS2
Motor Resistance
Closed Throttle Status
0.2~0.8V
4.2~4.8V
1.2~1.8?
Wide Open Throttle
(After starting engine)
Scan Tool Parameter
TPS VOLTAGE 1
TPS VOLTAGE 2
Normal value with ignition "ON" & engine "OFF"
Accelerator pedal released
Normal value with engine ON & accelerator pedal fully depressed
Abnormal value with ignition "ON" & engine "OFF"
Power circuit(#2) open
0.01V
0.00V
Ground cicuit(#1) open
4.99V
TPS1 signal circuit(#4) open
-
TPS1 signal circuit(#4) short to ground
Approx. 0V
TPS1 signal circuit(#4) short to battery
Above 4.99V
TPS2 signal circuit(#5) open
TPS2 signal circuit(#5) short to ground
TPS2 signal circuit(#5) short to battery