The PCM provides a 5volt reference voltage to the Acceleration Position Sensor1(APS2). The PCM monitors reference voltage deviation from the power supply circuit of the APS2.
PCM sets DTC P0642 if the PCM detects reference voltage lower than threshold value.
Item
Detecting Condition
Possible Cause
Case 1
DTC
Strategy
Electrical check
Short to ground in power circuit
Poor connection or damaged harness
Faulty APS2
Enable
Conditions
IG "ON"
Threshold Value
Short to ground
APS power supply voltage_2 < 0.7 V
Case 2
IG ON
Sensor or wiring harness problem
0.7 V = APS power supply voltage_2 < 4.5 V
Diagnostic Time
0.1 sec.
Mil On Condition
1 Drive Cycle
Limp-Home
Forced limited power mode : The PCM limits opening angle of the throttle valve to max. 50% and engine torque to a certain pre-determined value.
After idle recognition, the PCM uses APS1 signal to calculate the current opening angle of the throttle valve.