The ECM provides a 5volt reference voltage to the Acceleration Position Sensor1(APS2). The ECM monitors reference voltage deviation from the power supply circuit of the APS2.
ECM sets DTC P0642 if the ECM detects reference voltage is lower than threshold value.
Item
Detecting Condition
Possible Cause
Case 1
DTC
Strategy
Short to ground
Short to ground in power circuit
Poor connection or damaged harness
Faulty APS
Enable
Conditions
IG "ON"
Threshold
Value
APS power supply voltage_2 < 0.7 V
Case 2
Electrical check
0.7 V = APS power supply voltage_2 < 4.5 V
Diagnostic Time
0.1 sec
Mil On Condition
1 driving cycle
Fail Safe
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.
After idle recognition, the ECM uses APS1 signal to calculate the current opening angle of the throttle valve.