P0221

CIRCUIT DESCRIPTION
The Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator position. There are three sensors located within the APP module that are scaled differently.

CONDITIONS FOR RUNNING THE DTC
^ The Powertrain Control Module (PCM) performs this Diagnostic Trouble Code (DTC) diagnostic continuously.
^ The ignition voltage is more than 6.4 volts.
^ The engine speed is more than 300 RPM.
^ No in-range faults for APP 1 or for APP 3-The PCM checks for high and low voltage faults.

CONDITIONS FOR SETTING THE DTC
^ The difference between APP 2 and APP 1 is more than 0.23 volts (PCM compares pre-scaled voltage (internal to PCM)).
^ The difference between APP 2 and APP 3 is more than 0.50 volts (PCM compares pre-scaled voltage, internal to PCM.
^ All of the diagnostic set conditions are met for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
^ 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 non-emission related diagnostic.
^ Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
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. The least likely is a PCM problem.

An intermittent may be caused by the following:
^ Poor connections
^ Rubbed through wire insulation
^ Broken wire inside the insulation

A scan tool reads the APP 2 position in volts and should read about 4.5 volts with the throttle closed and the ignition ON or at idle. The voltage should decrease at a steady rate as the throttle is moved toward WOT. Also, 90 percent pedal travel is acceptable for correct APP operation. Scan the APP 2 sensor while depressing the accelerator pedal with the engine OFF and with the ignition ON. The display should vary from about 4.5 volts when the throttle is closed to about 1.5 volts when the throttle is held at Wide Open Throttle (WOT).

TEST DESCRIPTION

Steps 1-12:

The numbers below refer to the step numbers on the diagnostic table.
4. This step determines if there is a good 5-volt reference.
5. This step will check for an open in the ground circuit.