P1285

CIRCUIT DESCRIPTION
The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within one housing. Three separate signal, low reference and 5 volt reference circuits connect the APP 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 percent pedal travel (pedal at rest) to above 2.0 volts at 100 percent pedal travel (pedal fully depressed). The APP sensor 2 signal decreases from above 4.0 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal decreases from around 3.8 volts at 0 percent pedal travel to below 3.1 volts at 100 percent pedal travel. Notice that the signal circuits for APP sensor 2 and APP sensor 3 pull up to 5-volts and the APP sensor 1 signal circuit is referenced to low reference within the TAC module.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0606, P1517, or P1518 are not set.
^ The ignition is in the crank or run position.
^ The ignition voltage is greater than 5.23 volts.

CONDITIONS FOR SETTING THE DTC
^ The APP sensor 3 voltage is less than 01.63 volts or greater than 4.28 volts.
^ All 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.
^ Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
^ Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs could be set with no circuit or component conditions found during diagnostic testing.
^ When the TAC module detects throttle movement with a DTC P1285 set, a DTC P1286 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. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture Info.
^ For an intermittent, Refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-9:

Steps 10-18:

Steps 19-26:

The number below refers to the step number on the diagnostic table.
26. 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. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture Info.