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 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 3 APP
sensors disagree, or 1 APP sensor is out of range and the other 2 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 conditions occurs, multiple DTCs could set with no 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 condition is due to
the many redundant tests that continuously run on this system. Locating
and repairing 1 individual condition may correct more than 1 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
which are causing the APP sensor DTCs to set are corrected, the status of
this DTC will change to History.
