*CHECKING THE ACCELERATOR PEDAL POSITION SENSOR CALIBRATION





For a complete wiring diagram Refer to Section 8W



Possible Causes
APP SENSOR 1
APP SENSOR 2



Diagnostic Test

1. APP SENSOR IDLE VOLTAGE

NOTE: If there are any Accelerator Pedal Position Sensor DTC's active in the ECM, diagnose DTC's before continuing this test.


NOTE: The APP Sensor is a device that contains two separate potentiometer type sensors. Each sensor has its own 5-volt supply circuit, sensor ground circuit and signal circuit. The APP Sensor no longer incorporates a low-idle switch.


NOTE: The APP Sensor 1 signal should always be double the voltage of the APP Sensor 2 signal.


NOTE: Ensure the accelerator pedal is free from any restriction or binding before continuing.


Turn the ignition on.
With the scan tool, read the APP Sensor 1 and APP Sensor 2 Volts with the accelerator pedal in the at rest position.

Does the scan tool display between 0.38 and 0.53 volt for sensor 1 and 0.19 and 0.27 volt for sensor 2?

Yes


No

2. APP SENSOR 1

While back probing, measure the voltage of the APP Sensor 1 Signal circuit at the ECM.
Monitor the voltmeter while slowly pressing the accelerator pedal completely down.

NOTE: APP signals are displayed in voltage and percentage on the scan tool. Although APP 1 voltage is double APP 2 voltage, the percentage display of APP 1 and APP 2 should be within 2.5% of each other during all phases of accelerator pedal travel.



Did the voltage increase smoothly with pedal travel?

Yes


No

3. APP SENSOR 2

While back probing, measure the voltage of the APP Sensor 2 Signal circuit at the ECM.
Monitor the voltmeter while slowly pressing the accelerator pedal completely down.

NOTE: APP signals are displayed in voltage and percentage on the scan tool. Although APP 1 voltage is double APP 2 voltage, the percentage display of APP 1 and APP 2 should be equal during all phases of accelerator pedal travel.



Did the voltage increase smoothly with pedal travel?

Yes


No

4. APP SENSOR WIDE OPEN THROTTLE VOLTAGE

Fully depress the accelerator pedal.
With the scan tool, read the voltage for APP Sensor 1 and APP Sensor 2.

Does the scan tool display between 4.40 and 4.70 volts for sensor 1 and 2.20 and 2.35 volts for sensor 2?

Yes


No