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 B0790: Transfer Case Neutral Indicator Circuit Malfunction

Circuit/System Description

The Neutral indicator circuit consists of a ignition 3 voltage circuit and a Neutral indicator control circuit. When the Neutral mode has been selected by the driver, current is supplied to the Neutral indicator by the ignition 3 voltage circuit, traveling through the Neutral indicator LED at which time the transfer case shift control module supplies the ground through the Neutral indicator control circuit. This DTC indicates an open, short to ground or a short to voltage.

Conditions for Running the DTC

    • The ignition is ON.
    • The system voltage is 9-18 volts.

Conditions for Setting the DTC

    • The system monitors the voltage on the Neutral indicator control circuit.
    • If the system detects a voltage 3.5 volts or less when the Neutral indicator is not commanded, the DTC is logged.
    • If the system detects a voltage 3.5 volts or more when the Neutral indicator is commanded, the DTC is logged.

Action Taken When the DTC Sets

The SERVICE 4WD indicator will remain 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 33 consecutive ignition cycles without a fault present.
    • History DTCs can be cleared using a scan tool.

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.