GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC C0327: Encoder Circuit Malfunction

Circuit/System Description

The transfer case encoder is an analog sensor that returns a signal that represents the physical position of the transfer case sector shaft. This signal represents the mode, or range, position that the transfer case is currently in. This sensor is made up of the following 3 circuits:

    • A 5 volt reference circuit
    • An encoder signal circuit
    • An encoder low reference circuit

This DTC detects an out of range reading from the encoder signal, a short to voltage on the 5 volt reference, encoder circuit.

Conditions for Setting the DTC

The transfer case shift control module has a predefined range in which the encoder feedback should stay within, which is 0.5-4.5 volts. The DTC sets if the encoder signal feedback falls out of this range.

Action Taken When the DTC Sets

    • All motor activity will stop and the transfer case lock will engage.
    • The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC

    • The transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • History DTCs can be cleared using a scan tool.

Diagnostic Aid

Check the mechanical condition of the shift lever detent shaft connected to the motor. If this shaft has too much mechanical play this can cause an under voltage or over voltage from the encoder causing the DTC to set.

Reference Information

Schematic Reference

Transfer Case Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transfer Case Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.