Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator
pedal assembly. The sensor is actually three individual APP sensors within
one housing. Three separate signal, low reference, and 5-volt reference
circuits are used in order to connect the accelerator pedal sensor assembly
and the throttle actuator control (TAC) module. If only one APP sensor
diagnostic trouble code (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 one APP sensor. 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. However, if two or more DTCs are set
involving more than one 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 three APP sensors
disagree or one APP sensor is out of range and the other two APP sensors disagree. |
| • | All of the above conditions are 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.
When this occurs, multiple DTCs could be set with no circuit or component
conditions found during diagnostic testing. |
| • | The APP sensor 1 and the 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 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. |
Test Description
The number below refers to the step number on the diagnostic table.
-
When the problems
causing the APP sensor DTCs to set are corrected , the status of this DTC
will change to History.
