P1280

Schematic:

CIRCUIT DESCRIPTION
The Accelerator Pedal Position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The APP sensor is located on a bracket above the accelerator pedal. The Engine Control Module (ECM) supplies a separate 5 voltreference and the ground circuit for each of the sensors. The 5 voltreference for APP sensor 1 is supplied from the same source in the ECM as the 5 volt reference for the mass air flow sensor and the fuel tank pressure sensor. The 5 volt reference for APP sensor 2 is supplied from the same source in the ECM as the 5 volt reference for the throttle position sensors. The 5 volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to the shared voltage supply. The APP sensor sends a signal from each of the sensors to the ECM indicating the acceleration demand of the driver. The ECM actuates the throttle plates based on this information.

The APP sensor 1 signal voltage increases as the throttle opens, from about 0.4 volt at closed throttle to above 3.5 volts at wide open throttle. The APP sensor 2 signal voltage also increases as the throttle opens, but at a slightly different rate. The APP sensor 2 signal voltage increases from about 0.2 voltat closed throttle to about 1.8 volts at wide open throttle. The APP sensor 1 is the main control of the system. The APP sensor 2 is used for comparison of the APP sensor 1. The ECM constantly monitors these two sensors and if the sensors are not within a calibrated value, a Diagnostic Trouble Code (DTC) will set.

CONDITIONS FOR RUNNING THE DTC
The battery voltage is more than 7 volts.

CONDITIONS FOR SETTING THE DTC
^ The APP sensor 2 voltage is more than 4.8 volts or less than 0.2 volt.
or
^ The voltage of APP sensor 1 is 0.2 volt more than expected in part throttle range or 1.0 volt more than expected in full throttle range.

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.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The ECM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and passes.
^ 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 scan tool clears the MIL/DTC.

DIAGNOSTIC AIDS
The ECM compares the signal of each of the accelerator pedal position sensor to each other throughout the entire range of operation. Clear the DTCs and actuate the throttle through the entire range with the ignition ON and the engine OFF. If the DTC resets, check all of the circuits to the APP sensors for high resistance. Resistance as low a 2 ohms in the APP sensor circuits can affect the operation of the sensors.

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, test the sensor circuits for high resistance or shorts. Refer to Circuit Testing in Diagrams. If the circuits are OK, replace the APP sensor.

Use the J 35616-A connector test adapter kit for any test that requires probing the ECM harness connector or a component harness connector Using this kit will prevent damage to the harness connector terminals.

Refer to Testing for Intermittent and Poor Connections in Diagrams for Intermittent conditions.

TEST DESCRIPTION

Steps 1 - 6:

Steps 7 - 18:

Steps 19 - 25:

The numbers below refer to the step numbers on the diagnostic table.
2. The APP sensor 2 and the throttle position sensors all share the same 5 voltsource in the ECM. A short to ground or to voltage on the 5 voltreference circuit for the TP sensor will affect the operation of APP sensor 2.
5. The ECM performs a comparison of the signals from both APP sensors during the entire range of operation. If the DTC does not set with the key ON and the accelerator pedal released, actuating the throttle may cause the DTC to set.
8. This step is to test the integrity of the APP sensor 2 signal circuit.The APP sensor 2 data parameter on the scan tool should read near 5 volts when connected to the 5 voltreference circuit.
17. The 5 voltreference for the TP sensors and APP sensor 2 are connected inside the ECM. A short to voltage on the TP sensor 5 volt reference circuit will affect the operation of APP sensor 2