GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2003 🢒 H2 🢒 DTC 🢒 DTC C0359

Circuit Description

The 4WD LO circuit is used to notify the powertrain control module (PCM) that the vehicle is in 4WD low range. The PCM supplies 12 volts to this circuit. The transfer case shift control module grounds this circuit when the vehicle is in 4WD low range.

This DTC detects a short-to-ground, short-to-voltage, or an open in the 4WD LO circuit.

Conditions for Running the DTC
    • Ignition is ON.
    • System voltage is 9-18 volts.

Conditions for Setting the DTC
    • After the transfer case shift control module grounds the output, the 4WD LO circuit, and reads back a high voltage, the DTC is set. The system will not attempt setting the DTC again during that ignition cycle.
    • The transfer case shift control module reads back a high voltage when a low voltage is expected on the 4WD LO circuit.

Action Taken When the DTC Sets
    • Transmission shift points may be affected.
    • The SERVICE 4WD indicator will be latched on 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 proper reference voltage to the transfer case shift control module on the 4WD LO circuit.

    2.

  2. Tests the 4WD Low circuit for a short-to-voltage.

    3.

  3. Tests the 4WD Low circuit for an open or high resistance.

    4.

  4. Repairs the 4WD Low circuit for a short-to-voltage.

Step

Action

Values

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. Disconnect the transfer case shift control module.
  3. Turn the ignition ON, with the engine OFF.
  4. Measure the voltage between the 4WD LO circuit harness and ground.

Is the voltage reading within the specified values?

10-13.5 V

Go to Step 3

Go to Step 4

3

  1. Disconnect the PCM.
  2. Measure the voltage between the 4WD Low circuit harness and ground.

Is the voltage reading within the specified value?

0 V

Go to Step 7

Go to Step 5

4

Test the 4WD LO circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 6

5

Repair the 4WD LO circuit for short-to-voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

--

6

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine controls 6.0L (LQ4).

Did you complete the repair?

--

Go to Step 8

--

7

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

Did you complete the repair?

--

Go to Step 8

--

8
  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 2

System OK