DTC C0327. GMC Truck TopKick C-Series (Conventional) C6/C7/C8 2007

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC C0327

Circuit 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:

•	5-volt reference circuit

•	Encoder signal circuit

•	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 circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0327 Encoder Circuit Malfunction

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

•	All motor activity stops.

•	The SERVICE 4WD indicator is not illuminated.

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.

Test Description

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

This step checks for a voltage reading on the scan tool.

This step tests the encoder circuit for a current malfunction.

This step tests for an internal encoder malfunction which is present only in certain areas of the encoder sensor.

This step tests for proper reference voltage at the encoder.

This step tests the 5-volt reference circuit for proper voltage when the low reference circuit is used as a ground.

This step tests the 5-volt reference encoder circuit for a short to voltage, short to ground, an open or high resistance.

This step helps determine whether the encoder signal circuit is being pulled high or low.

This step tests the encoder signal circuit and the encoder low reference circuit for a short to voltage.

This step helps determine a faulty encoder.

This step tests the encoder signal circuit and the encoder low reference circuit for an open or a short to ground.

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 - Vehicle?	--	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install a scan tool. Turn the ignition ON with the engine OFF. With a scan tool, observe the different voltage parameters. Are the voltage parameters displayed?	--	Go to Step 3	Go to Step 5
3	Install a scan tool. Start the engine. Set the park brake. Place the transmission in Neutral. With a scan tool, observe the Encoder Return Voltage parameter. Select each of the mode positions. Does the voltage reading stay within the specified values?	0.5-4.5 V	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 4
4	Does the voltage reading stay within the specified values at any position?	0.5-4.5 V	Go to Step 13	Go to Step 5
5	Turn the ignition OFF. Disconnect the encoder motor. Turn the ignition ON with the engine OFF. Measure the voltage from the 5-volt reference encoder circuit to a good ground. Does the voltage measure within the specified values?	4.8-5.2 V	Go to Step 6	Go to Step 8
6	Test the low reference circuit by using a DMM to measure voltage from the 5-volt reference circuit pin A to the low reference circuit pin C at the encoder pigtail on the module side of the harness. Does the voltage reading stay within the specified values?	4.8-5.2 V	Go to Step 9	Go to Step 7
7	Test the low reference circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 15	Go to Testing for Intermittent Conditions and Poor Connections
8	Test the 5-volt reference encoder circuit for a short to voltage, short to ground, an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
9	Was the voltage reading measured in Step 4 greater than 5.2 volts?	--	Go to Step 10	Go to Step 11
10	Test the encoder signal circuit and the encoder low reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
11	Install a scan tool. Turn the ignition ON with the engine OFF. Using a fused jumper, probe between the 5 volt reference encoder circuit and encoder signal circuit. With a scan tool, observe the Encoder Return Voltage parameter. Is the encoder return voltage display within the specified values?	4.8-5.2 V	Go to Step 13	Go to Step 12
12	Test the encoder signal circuit and the encoder low reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
13	Replace the transfer case actuator assembly. Refer to Transfer Case Actuator Assembly Replacement . Did you complete the repair?	--	Go to Step 15	--
14	Replace the transfer case shift control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the repair?	--	Go to Step 15	--
15	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC set?	--	Go to Step 2	System OK