P1280

CIRCUIT DESCRIPTION
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within 1 housing. Three separate signal, low-reference and 5-volt reference circuits connect the APP sensor assembly to the throttle actuator control (TAC) module. Each sensor has a unique functionality.

The throttle position (TP) sensor 1 and APP sensor 1 share a 5-volt reference circuit that are connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that are connected within the TAC module. If only 1 APP sensor DTC is set, the redundant APP systems allow the TAC system to continue operating normally. One APP sensor DTC will not cause the Reduced Engine Power message to be displayed. Two APP sensor DTCs for the same sensor also will not cause the Reduced Engine Power message to be displayed. If an out of range condition is detected with this APP sensor, this DTC will be set.

APP Sensor Position Table:

The table shows the percentage and voltage readings of the scan tool based on the position of the APP.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0601, P0602, P0606, P1517, or 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 is less than 0.83 volt or greater than 4.81 volts.
^ All of the above conditions are present for less than 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The control module stores the DTC information into memory when the diagnostic runs and fails.
^ The malfunction indicator lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ If one or more APP sensor DTCs are set for a single APP sensor, the following occurs:
- The control module will not command Reduced Engine Power mode.
- The control module will use the remaining two APP sensors to calculate throttle response.
^ If certain multiple APP sensor DTCs are set for more than one APP sensor, the following occurs:
- The control module commands Reduced Engine Power mode.
- The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.
- The message center displays Reduced Engine Power.
^ If all three APP sensors are out of range, the following occurs:
- The control module commands Reduced Engine Power mode.
- The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.
- The message center displays Reduced Engine Power.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC Last Test Failed clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ Clear the DTC with a scan tool.

DIAGNOSTIC AIDS
^ Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
^ 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 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
^ For an intermittent, refer to Intermittent Conditions.

TEST DESCRIPTION

Steps 1-9:

Steps 10-18:

Steps 19-26:

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-volt reference source. Diagnosis DTC P1220 first if P1220 is also set.
18. This test determines whether or not the TAC module can recognize a change in signal voltage.
19. There are 3 separate 5-volt reference sources within the TAC module. TP sensor 1 and APP sensor 1 share 1 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 1 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.
26. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.