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. |
| • | P1635, P1277, P1278, P1282, and P1283 are not set. |
| • | The ignition voltage is greater than 8 volts. |
Conditions for Setting the DTC
| • | The difference between the APP 1 sensor and the APP 2 sensor is
greater than 16 percent [PCM compares pre-scaled voltage (internal
to PCM)]. |
| • | All of the diagnostic 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 stores 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 cause is a PCM.
An intermittent may be caused by the following:
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
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.
A scan tool reads APP 2 position in volts and should read about 4.5 volts
with throttle closed and ignition ON or at idle. Voltage should decrease at
a steady rate as throttle is moved toward WOT. Also, 90 percent
pedal travel is acceptable for correct APP operation. Scan APP 2 sensor
while depressing accelerator pedal with engine stopped and ignition
ON. Display should vary from about 4.5 volts when throttle
was closed to about 1.5 volts when throttle is held at wide
open throttle (WOT) position.
