P1280

Circuit Description
The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually three individual Accelerator Pedal Position sensors within one housing. Three separate signal, ground and 5 volt reference circuits connect the Accelerator Pedal Position Sensor assembly and the Throttle Actuator Control (TAC) Module. Each sensor has a unique functionality. The APP sensor 1 signal increases as the accelerator pedal is depressed, from below 1.0 volt at 0% pedal travel (pedal at rest) to above 2.0 volts at 100% pedal travel (pedal fully depressed). The APP sensor 2 signal decreases from above 4.0 volts at 0% pedal travel to below 2.9 volts at 100% pedal travel. The APP sensor 3 signal decreases from around 3.8 volts at 0% pedal travel to below 3.1 volts at 100% pedal travel. Observe that the signal circuits for APP Sensor 2 and APP Sensor 3 pull up to 5 volts and the APP Sensor 1 signal circuit referenced to ground within the TAC Module.

Conditions for Running the DTC
^ DTCs P0601, P0602, P0606, P1517, P1518 are not set.
^ The ignition switch is in the crank or run position.
^ The ignition voltage is greater than 5.23 volts.

Conditions for Setting the DTC
^ The APP sensor 2 voltage ranges between 0.83 volts and 4.81 volts
^ All of the above conditions met for less than 1 second.

Action Taken When the DTC Sets
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.
^ If no other TAC System DTCs are set, the TAC System operates normally. If certain TAC System DTCs are set at the same time, the TAC System either defaults to a Reduced Engine Power mode or to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shut down.

Conditions for Clearing the MIL/DTC
^ A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
^ The following may cause an intermittent:
- Poor connections
- Corrosion
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- Inspect the TAC module connectors for signs of water intrusion. This causes intermittent DTCs.
^ The APP sensor 1 and the TP sensor 1 5.0 volt reference circuits are internally connected within the TAC.
^ The APP sensor 2 and the TP sensor 2 5.0 volt reference circuits are internally connected within the TAC.
^ When the TAC module detects throttle movement with a DTC P1280 set, a DTC P1281 also sets.
^ When the TAC module detects a condition within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.
^ For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
2. TP sensor 2 and the APP sensor 2 share a common 5.0 volt reference source. Diagnosis DTC P1220 first if it is also set.
18. This test determines whether or not the TAC Module can recognize a change in signal voltage.
19. here are three separate 5 volt reference sources within the TAC Module. TP Sensor 1 and APP Sensor 1 share one 5 volt reference source, TP Sensor 2 and APP Sensor 2 share another common 5 volt reference source and APP Sensor 3 uses the third by itself. This test determines whether the signal circuit is shorted to any one of the 5 volt reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.
20. The previous step found the signal circuit and a 5 volt reference circuit shorted together. This test isolates whether the short is in the harness or within the TAC Module.
35. When a condition is detected within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. It is possible that locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.