GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Yukon - 4WD 🢒 DTC 🢒 DTC B0790

Circuit 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
    • Ignition is ON.
    • 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.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for voltage at the ignition 3 voltage side of the transfer case select switch.

    2.

  2. Tests the control circuit of the neutral indicator for a short to voltage or an open.

    3.

  3. Tests the control circuit of the neutral indicator for a short to ground.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

Connector End View Reference: Transfer Case Control Connector End Views

1

Did you perform the Diagnostic System Check-Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2
  1. Turn the ignition OFF.
  2. Remove the transfer case select switch.
  3. Disconnect the connector on the transfer case select switch.
  4. Turn the ignition ON.
  5. Probe the Ignition 3 voltage circuit with a DMM that is connected to a good ground.

Does the DMM indicate battery voltage?

Go to Step 3

Go to Step 6

3

Test the neutral indicator control circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 4

4

Test the neutral indicator control circuit for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 5

5

Inspect for poor connections at the harness connector of the transfer case shift control module, and the transfer case shift control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 7

6

Repair the ignition 3 voltage circuit of the transfer case select switch for an open, high resistance or short to ground.

Did you complete the repair?

Go to Step 9

--

7

Replace the transfer case shift control switch, and clear all DTCs. Refer to Transfer Case Shift Control Switch Replacement .

Does the DTC reset?

Go to Step 8

System OK

8

Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .

Did you complete the repair?

Go to Step 9

--

9
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 1

System OK