GM/Detroit 6.5L ENGINE CONTROLS – DTC P0228 APP Sensor3 Circuit High Voltage

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.
• The ignition switch in the ON position.

Conditions for Setting the DTC
• The signal voltage on the APP 3 sensor is more than 4.75 volts.
• All diagnostic conditions met for 2 seconds.

Action Taken When the DTC Sets
• The input from APP 3 sensor is ignored.
• This DTC will not turn on the Service Throttle Soon lamp by itself.
• The throttle will operate normally as long as there is only one malfunction present. If two different APP sensors have a malfunction, the Service Throttle Soon lamp will light and the PCM will limit power. If three APP sensors have a malfunction present, the Service Throttle Soon lamp will light and the PCM will only allow the engine to operate at idle.

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
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.
A scan tool reads APP 3 position in volts. It should read about 4.0 volts with the throttle closed and the ignition ON or at idle. Voltage should decrease at a steady rate as the throttle is moved toward wide open throttle (WOT). Also, 90% pedal travel is acceptable for correct APP operation. Scan APP 3 sensor while depressing the accelerator pedal with the engine off and the ignition ON. Display should vary from about 4.0 volts when the throttle is closed to about 2.0 volts when the throttle is held at wide open throttle (WOT).

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. This step determines if PO228 is a hard failure or an intermittent condition.
5. This step will check for an open in the ground circuit.


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