V6 EngineAJ-V6/AJ28
27
D.418.428
APP Sensor
303-050
APP SENSORAccelerator Pedal Position (APP)
Sensor
The APP sensor is driven directly by the pedal
pivot shaft and is connected via the wiring
harness to the powertrain control module (PCM).
The sensor is a single assembly comprising three
rotary, carbon track potentiometers with
contacting wipers. Each potentiometer has a
discrete 5V reference/return supplied from the
PCM and provides an independent analogue
output voltage to the PCM. As described for the
TP sensor, the characteristics of the three
potentiometers (angle/output voltage) differ so as
to provide unique identification to the PCM. Note
that while the TP and APP sensor characteristics,
as shown, have a general similarity, actual values
of voltage, slope and angular range for each type
of sensor is different.
Further system redundancy is provided by the use
of two pedal return springs.
Control and Operation
Drive Motor Control
The PCM does not drive the throttle motor
directly but sends duplicated control signals to the
TAC module indicating the desired throttle plate
angle. Both signals are pulse width modulated
(PWM) at 256Hz with an increase in duty cycle
indicating a corresponding (linear) increase in
desired throttle angle (ie towards full throttle).
Separate interface circuits within the PCM and
TAC module provide additional signal redundancy.
In response to PCM demand, the TAC module
processes the demand signals and generates the
current drive to the dual winding motor. An
inductive position encoder on the motor shaft
generates feedback signals to the TAC module,
providing closed loop motor control and enabling
the TAC module to maintain the desired angle.
Actual throttle plate angle is measured by the TP
sensor.
The TAC module has two separate feeds from the
vehicle 12V and ground supply, each feed (12V
and ground) being a twisted pair to reduce noise
pick up.
The TAC module also performs self diagnostic
checks:
¥ the two PWM control signals are compared
for validity
¥ the ability of the TAC module to set the
requested throttle angle is monitored¥ operation of the motor drive circuit is
checked
¥ a failed throttle return spring can be detected
¥ failure of one or both motor windings can be
detected
¥ the output of the inductive position encoder
is checked for out of range signals or failure
Diagnostic information from the TAC module is
communicated to the PCM over the twisted pair
SCP link.
