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 APS is mounted in the accelerator pedal to detect the opening angle of the accelerator pedal. It has 2 sensors to detect the accelerator position and a malfunction of the accelerator position sensor. The ECM judges the current opening angle of the accelerator pedal from APS1&2, and the ECM controls the throttle motor based on these signals.
ECM sets DTC P2138 if the ECM detects output voltage of the APS1 is not proportion to APS2
Item
Detecting Condition
Possible Cause
DTC Strategy
? Plausibility check
? Poor connection or damaged harness
? APS1
? APS2
Enable Conditions
Case1
? No relevant failure
Case2
? APS1 >1.0V or APS2 >0.55V
Threshold Value
? One channel of APS is moving and other channel is not reaching threshold
? Ratio error between APS1 & APS2
Diagnostic Time
? 0.10sec.
? 0.35sec.
Limp-Home
? Forced limited power mode : The ECM limits opening angle of the throttle valve to max. 50% and engine torque to a certain pre-determined value.
? The ECM selects the current opening angle of the throttle valve from minimum value of APS1 and APS2
Test Condition
Scan Tool Parameter
Scan Tool Screen
ACCEL PEDAL VOLT-1
ACCEL PEDAL VOLT-2
Normal value with ignition "ON" & engine "OFF"
APS 1&2 output voltage increases smoothly in proportion with the depressing acceleration pedal amount. The output voltage of the APS2 is half of the APS1
Fig. 1
Accelerator pedal released
Approx. 0.58~0.93V
Approx. 0.29~0.38
Fig. 2
Accelerator pedal fully depressed
Approx. 3.85~4.35V
Approx. 1.93~2.18V
Fig. 3
Abnormal value with ignition "ON" & engine "OFF"
APS1 power circuit open
Approx. 0.00V
-
Fig. 4
APS1 ground circuit open or signal circuit short to battery
Approx. 4.91V
Fig. 5
APS1 signal circuit open or short to ground
APS2 power circuit open
Fig. 6
APS2 ground circuit open or signal circuit short to battery
Approx. 4.78V
Fig. 7
APS2 signal circuit open or short to ground