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.
Checking output signals from APS 1 and 2 under detecting condition, if output signals difference between APS 1 and 2 are detected more than 4.5% for the specified number of times., ECM sets P2138.
Item
Detecting Condition
Possible cause
DTC Strategy
Plausibility check between pedal value sensor 1, 2
Poor connection
Open or short in APS circuit
Faulty APS
Faulty ECM
Enable Conditions
After Eng. Start
Threshold value
I (APS1/2) –APS2 I > Threshold f(Eng. rpm)
Diagnosis Time
0.16 sec
MIL On Condition
NO MIL
Pedal Position
Output Voltage(V) [Vref = 5.0V]
APS1
APS2
C.T
'0.7 ~ 0.8V
0.29 ~ 0.46V
W.O.T
'3.85 ~ 4.35V
1.93 ~ 2.18V
Fig.1) Normal waveform of APS1 & APS2 with acceleration
Signal waveform of APS 1 & 2 shows that APS 2 increases voltage just half of APS 1 voltage increase when accelerating.