Circuit Description
The accelerator pedal position (APP) module provides a voltage signal
that changes relative to accelerator pedal position. There are three sensors
located within the APP module that are scaled differently.
Conditions for Running the DTC
| • | The PCM performs this DTC diagnostic continuously. |
| • | DTCs P1635, P1646, P1277, P1278, P1287, and 1288 are not
set. |
| • | The ignition voltage is greater than 8 volts. |
Conditions for Setting the DTC
| • | The difference between APP 3 and APP 1 sensor is greater than
16 percent [PCM compares pre-scaled voltage (internal to the PCM)]. |
| • | All of the diangostic set conditions met for 2 seconds. |
Action Taken When the DTC Sets
| • | The service throttle soon lamp will not illuminate when only
one APP DTC is set. The PCM will only illuminate the service throttle soon
lamp when multiple APP DTCs are set. |
| • | The PCM records the operating conditions at the time the diagnostic
fails. This information is stored in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A History DTC clears after forty consecutive warm-up cycles, if
this or any other emission related diagnostic does not report any failures. |
| • | The use of a scan tool. |
Diagnostic Aids
Important: Remove any debris from the PCM module connector surfaces before servicing
the PCM module. Inspect the PCM module connector gaskets when diagnosing/replacing
the module. Ensure that the gaskets are installed correctly. The gaskets
prevent contaminate intrusion into the PCM module.
There are no driveability issues associated with the APP module unless
a DTC is present. The most likely causes of this DTC are poor connections
or the sensor itself. The least likely is a PCM problem.
An intermittent may be caused by the following conditions:
| • | Poor connections (terminal tension) |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
A scan tool reads APP 3 position in volts. Should read about
4.0 volts with throttle closed and ignition ON or at idle. Voltage
should decrease at a steady rate as throttle is moved toward wide
open throttle (WOT). Also, 90 percent pedal travel is acceptable
for correct APP operation. Scan APP 3 sensor while depressing
accelerator pedal with engine stopped and ignition ON. Display
should vary from about 4.0 volts when throttle was closed to
about 2.0 volts when throttle is held at wide open throttle
(WOT) position.
A scan tool reads APP 1 position in volts. It should read about
0.45 to 0.95 volt with throttle closed and ignition ON or at idle.
Voltage should increase at a steady rate as throttle is moved toward
wide open throttle (WOT). Also, 90 percent pedal travel is
acceptable for correct APP operation. Scan APP 1 sensor while
depressing accelerator pedal with engine stopped and ignition ON.
Display should vary from about 0.74 volt when throttle was closed
to over about 3.7 volts when throttle is held at wide open
throttle (WOT) position.
