Powertrain Controls - ECM/PCM

DTC 27 Accelerator Pedal Position (APP) 2 Circuit Range Fault:

Accelerator Pedal Position (APP):

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.

DIAGNOSTIC TROUBLE CODE (DTC) 27 WILL SET WHEN
Powertrain Control Module (PCM) has recognized a "skewed" (mis-scaled) sensor. The PCM compares all three sensors to each other (percentage to voltage chart) and determines if there is a 6% difference between APP 1 and APP 2 and a 10% difference to APP 3.

ACTION TAKEN (PCM will default to)
The input from APP 2 sensor is ignored. A current and history DTC will set but it will not turn "ON" the "Service Throttle Soon" lamp. Throttle will operate normally as long as there is only one malfunction present If there are two APP malfunctions present, the PCM will then turn "ON" the "Service Throttle Soon" lamp and limit power. If a third APP malfunction is present, the "Service Throttle Soon" lamp will be "ON" and will only allow the engine to operate at idle.

DTC 27 WILL CLEAR WHEN
The fault condition(s) no longer exist. and the ignition switch is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if there is a good 5 volt reference.
2. This step will check for an open in the ground circuits.

DIAGNOSTIC AIDS
A Tech 1 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% pedal travel is acceptable for correct APP operation.
Refer to Intermittents. - Intermittent Malfunctions
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.