Hummer H2. Manual - part 2654

DTC C0327

Circuit Description

The transfer case shift control module has four encoder channels, P, C, A, and B, which are supplied 5 volts
each. The four encoder channels each run to a switch located inside the encoder/motor assembly. When a
particular encoder channel is active the switch is closed and 5 volts flows through the encoder signal return
circuit. If the module wants to request motor position a low side driver pulls the voltage low on the encoder
signal return and the corresponding channel circuit indicating motor position.

The transfer case shift control module supplies 5 volts on all encoder channels, thus as these channels are pulled
to ground, the module can interpret the location of the transfer case shift position.

This DTC detects an open, high resistance, or a short to voltage, in the encoder signal return circuit, or an open,
high resistance, or short to voltage in the encoder channel circuits.

Conditions for Running the DTC

The ignition is ON.

The system voltage is 9-18 volts.

Conditions for Setting the DTC

The transfer case shift control module reads back a high voltage when a low voltage is expected, or low voltage
when a high voltage is expected on the encoder channel circuits, or the encoder signal return circuit.

Action Taken When the DTC Sets

All motor activity will stop.

All the transfer case shift control switch mode indicators will be commanded OFF.

The SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.

If a new mode is requested while the DTC is present either current or history, the indicator for the mode
requested will flash for 15 seconds and then go out.

Conditions for Clearing the DTC

The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer
exists.

A history DTC will clear after 33 consecutive ignition cycles without a fault present.

1. Use the scan tool in order to clear the DTCs.

2. Operate the vehicle within the Conditions for

Setting the DTC as specified in the supporting text.

Does the DTC reset?

Go to

Step 2

System OK

2004 Hummer H2

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

History DTCs can be cleared using a scan tool.

Test Description

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

2: This step determines if 2 or more of the 5 volts encoder signal circuits are shorted together.

3: This step tests for proper voltage on the 4 encoder signal circuits.

4: This step tests for a short to voltage, open, or high resistance on the encoder low reference circuit.

5: This step determines which encoder signal circuits are shorted together.

6: This step determines if any of the encoder signal circuits have an open, or high resistance condition.

7: This step determines if a binding shift detent lever shaft is causing the DTC.

DTC C0327

Step

Action

Value

(s)

Yes

Schematic Reference: Transfer Case Control Schematics
Connector End View Reference: Transfer Case Control Connector End Views

Did you perform the Diagnostic System Check - Transfer
Case?

Go to

Step 2

Go to Diagnostic

System Check -

Transfer Case

1. Set the parking brake.

2. Raise the vehicle on a hoist.

3. Disconnect the connector at the transfer case.

4. Turn the ignition ON, with the engine OFF.

5. Install a scan tool.

6. While monitoring the encoder channels on the scan tool,

short to ground each of the encoder channel circuits on
the module side of the harness with a jumper wire.

Do more than one of the four encoder channels indicate OFF
when each encoder channel circuit is individually shorted to
ground?

Go to

Step 5

Go to Step 3

At the transfer case connector, using a digital multimeter
(DMM), test the encoder signal circuits on the module side of
the harness.
Are the voltages within the specified range?

4.3-

4.7 V Go to

Step 4

Go to Step 6

With the ignition in the OFF position, test the encoder low
reference circuit for a short to ground, short to voltage, open, or
high resistance. Refer to Circuit Testing and Wiring Repairs
in Wiring Systems.
Did you find and correct the condition?

Go to

Step

Go to Step 7

2004 Hummer H2

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

DTC C0329

Circuit Description

The transfer case shift control module has 4 encoder channels coming out of it which are all supplied 5 volts.
These 4 channels are P, C, A, and B, each running to a switch located inside the encoder/motor assembly. When
a particular encoder channel is active, the switch is closed and 5 volts flows through the encoder signal return
circuit. If the module wants to request motor position, a low side driver pulls the voltage low on the encoder
signal return and the corresponding channel circuit indicating motor position.

The transfer case shift control module supplies 5 volts on all the channels. As these channels are pulled to
ground, the module can interpret the location of the transfer case shift position.

1. Disconnect C1 and C2 from the transfer case shift

control module.

2. Using a DMM, test for 2 or more encoder signal circuits

being shorted together. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to

Step

Go to Step 10

Test the suspect circuits for a short to ground, short to voltage,
open, or high resistance. Refer to Circuit Testing and Wiring
Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step

Go to Step 10

1. Remove the encoder motor.

2. Inspect the shift detent lever shaft for a binding

condition. Refer to Transfer Case Motor/Encoder
Replacement .

Did the shift detent lever shaft bind?

Go to

Step 8

Go to Step 9

Remove the transfer case for disassembly and repair. Refer to
Transfer Case Disassemble .
Did you complete the repair?

Go to

Step

Replace the encoder motor. Refer to Transfer Case
Motor/Encoder Replacement .
Did you complete the repair?

Go to

Step

Replace the transfer case shift control module. Refer to
Transfer Case Shift Control Module Replacement .
Did you complete the repair?

Go to

Step

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 set?

Go to

Step 1

System OK

2004 Hummer H2

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

This DTC detects a short to ground in the encoder signal return circuit, or a short to ground in the encoder
channel circuits.

Conditions for Running the DTC

The ignition is ON.

The system voltage is 9-18 volts.

Conditions for Setting the DTC

The transfer case shift control module can command the low side driver on the encoder signal return circuit not
to pull the signal low. The module can then read the voltage on each of the encoder channel circuits. If the
voltage is low a short to ground is indicated and the DTC is logged.

Action Taken When the DTC Sets

All motor activity will stop.

All the transfer case shift control switch mode indicators will be commanded OFF.

The SERVICE 4WD indicator will be commanded ON, and an active DTC set, when a shift is requested.

If a shift is not being requested the DTC will go to history.

If a new mode is requested while the DTC is present either current or history, the indicator for the mode
requested will flash for 15 seconds and then go out.

Conditions for Clearing the DTC

The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer
exists.

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.

2: This step determines if one or more of the encoder channel circuits are shorted to ground.

3: This step checks with a digital multimeter (DMM) for a short to ground on any of the 4 encoder
channel circuits.

4: This step checks the encoder sign return circuit for a short to ground.

5: This step determines if a faulty transfer case shift control module is causing the DTC to set.

6: This step determines if the encoder motor is causing the DTC to set.

DTC C0329

Step

Action

Value

(s)

Yes

2004 Hummer H2

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

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