P1271

Circuit Description
The Accelerator Pedal Position (APP) sensors are two sensors that are housed inside one assembly. The ECM supplies the 5 volt reference and the ground circuit for both of the sensors. The APP 1 sensor sends a signal to the ECM of the drivers demand. The ECM then calculates the proper spark and PWM fueling.

The APP 1 sensor is the main control of the system. The APP 2 sensor is used for comparison of the APP 1 sensor. The ECM constantly monitors these two sensors and if the sensors are not within a calibrated value a DTC will set.

Conditions for Running the DTC
The battery voltage is more than 7 volts.

Conditions for Setting the DTC
This DTC will set if the voltage difference between accelerator pedal position (APP) sensor 1 and APP sensor 2 is not correct when leaving idle.

Action Taken When the DTC Sets
The ECM illuminates the Malfunction Indicator Lamp (MIL) and records the operating conditions in the Freeze Frame on the first drive trip that the diagnostic runs and fails. The vehicle will default to the limp home mode.

Conditions for Clearing the MIL/DTC
^ The ECM turns off the MIL after 3 consecutive drive trips that the diagnostic runs and does not fail.
^ A History DTC clears after 40 consecutive warm up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
^ The ECM battery voltage is interrupted.
^ The scan tool clears the MIL/DTC.

Diagnostic Aids
With the ignition ON and the engine OFF view the APP sensor 1 and the APP sensor 2 with a scan tool. Slowly depress the accelerator pedal, if one sensor value changes and the other does not, inspect the sensor circuits for high resistance or shorts. If the circuits are OK, replace the APP sensor.

Notice: Refer to J 35616-A Connector Test Adapter kit Notice in Service Precautions.

Use the J 35616-A Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Check for the following conditions:
^ Poor connections at the ECM or at the component-Inspect the harness connectors for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Poor terminal to wire connection
^ Damaged harness-Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or the connections, the component may be damaged.
Refer to Symptoms for the Intermittents.
^ Inspect the APP sensor mounting bolts and actuator arm. The bolts should be tight. If the APP sensor is loose, a false reading could be sent to the ECM. Symptom Related Diagnostic Procedures