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, ground and 5 volt
reference circuits are used to connect the accelerator pedal sensor
assembly and the throttle actuator control (TAC) module. If only
one APP sensor DTC is set, the redundant APP systems allow
the TAC system to continue operating normally. This DTC sets if
the PCM detects a problem 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. The Reduced Engine Power message
is displayed.
Conditions For Running the DTC
| • | DTCs P1517, P1518 are not set. |
| • | Ignition in the crank or run position. |
| • | Ignition voltage more than 5.23 volts. |
Conditions for Setting the DTC
| • | Two or more APP sensors are out of range. |
| • | All 3 APP sensors disagree. |
| • | One APP sensor is out of range and the other 2 APP sensors
disagree. |
| • | All above conditions met for less than 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) and
the Reduced Engine Power light will be on when the diagnostic fails. |
| • | The PCM will record operating conditions at the time the diagnostic
fails. This information will be stored in the Freeze Frame and Failure
Records. |
| • | If no other TAC System DTCs are set, the TAC System will operate
in Reduced Engine Power mode, and this DTC will be stored. If certain TAC
System DTCs are set at the same time, the TAC System will either
default to a more tightly restricted mode of operation if it
is determined that limited safe operation is possible, or command
engine shut down. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after 3 consecutive drive
trips that the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles,
if no failures are reported by this or any other emission related
diagnostic. |
| • | A last test failed (Current DTC) will clear when the diagnostic
runs and does not fail. |
| • | PCM battery voltage is interrupted. |
| | Important: The clear DTC info function may have to be performed twice in order
to clear a throttle actuator Control System DTC.
|
Diagnostic Aids
| • | Inspect for the cause of intermittents. An intermittent may be
caused by the following conditions: |
| - | Inadequate terminal tension |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| • | Inspect for adequate terminal tension. Refer to
Wiring Repairs
in wiring systems. |
| • | Inspect the TAC module connectors for signs of water intrusion.
When this occurs, multiple DTCs should be set and no circuit or component
problems can be located. |
| • | If a repair is completed and the DTC was cleared using a scan
tool on the same ignition cycle, the default action will not clear until an
ignition cycle has occurred. |
| • | Inspect for further causes of intermittents. Refer to
Symptoms
. |
Test Description
The numbers below refer to the step numbers 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.
When the TAC module detects a problem 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
problem may correct more than one DTC. Keep this in mind when reviewing
captured DTC info.
