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 P0643 if the PCM detects reference voltage higher than threshold value.
Item
Detecting Condition
Possible Cause
DTC Strategy
Electrical Check
Short to battery in power circuit
Poor connection or damaged harness
Faulty APS2
Enable Conditions
IG "ON"
Threshold Value
Short to battery
APS2 >5.5V
Diagnostic Time
0.1sec.
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.