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 circuits are used in order to connect the accelerator pedal
sensor assembly, and the throttle actuator control (TAC) module:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
If only 1 APP sensor DTC is set, the redundant APP systems allow the
TAC system to continue operating normally. This DTC sets if the powertrain control
module (PCM) detects a condition with more than 1 APP sensor. One APP sensor
DTC will not cause the Reduced Engine Power message to be displayed. 2 APP
sensor DTCs for the same sensor also will not cause the Reduced Engine Power message
to be displayed. However, if two or more DTCs are set involving more than 1 APP
sensor, this DTC will set and the Reduced Engine Power message is displayed.
Conditions for Running the DTC
| • | DTCs 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
| • | Two or more APP sensors are out of range or all 3 APP sensors disagree
or 1 APP sensor is out of range, and the other 2 APP sensors disagree. |
| • | All of the above conditions present for less than 1 second. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when
the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic
fails. The control module stores this information in the Freeze Frame and/or the Failure
Records. |
| • | The control module commands the TAC system to operate in the
Reduced Engine Power mode. |
| • | A message center or an indicator displays Reduced Engine Power. |
| • | Under certain conditions the control module commands the engine OFF. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL)
after 3 consecutive ignition cycles that the diagnostic runs and does
not fail. |
| • | 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 emission related diagnostic. |
| • | Clear the MIL and 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. |
| • | The APP sensor 1 and the throttle position (TP) sensor 1,
5-volt reference circuits are internally connected within the TAC module. |
| • | The APP sensor 2 and the TP sensor 2, 5-volt reference
circuits are internally connected within the TAC module. |
| • | 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. Remember this if you review the information stored
in Captured Info. |
Test Description
The number below refer to the step number on the diagnostic table.
-
When the problems are corrected which are causing
the APP sensor DTCs to set, the status of this DTC will change to history.
