GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC 003

Circuit Description

This code indicates that the transfer case encoder motor circuits are not functioning properly. One of the following conditions may exist.

    • One of the internal power relays in the transfer case shift control module (TCCM) is not energizing or de-energizing.
    • An open exists in the Battery Positive Voltage, Ground, Motor Control A or Motor Control B circuits.
    • A short to ground exists in the Battery Positive Voltage, Motor Control A or Motor Control B circuits.
    • A short exists within the motor or TCCM.

The transfer case encoder motor has a bi-directional, permanent magnet, D.C. motor. When a shift request is made by the TCCM, voltage will be applied through one of the motor control circuits and the TCCM will provide the ground through the other motor circuit. When a shift is requested in the opposite direction, the TCCM will reverse polarity on these 2 circuits. The motor through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between gears.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC 003 Motor A or Motor B Circuit Malfunction

Action Taken When the DTC Sets

The TCCM utilizes an error counting system when setting this code. When the TCCM detects a circuit error, the counter will log a count of 4. When the system operates correctly, the counter will reduce by a count of 1. A total count of 32 must be reached in order for DTC 003 to be set. The system must malfunction at least 25 percent of the time in order for a DTC 003 to be set. It is imperative that the technician test drive the vehicle and request several shifts in order for this code to be properly logged.

In the event that one of the internal TCCM power relays is stuck in the energized state, the TCCM will energize the other motor control circuit to keep the motor from running. All of the transfer case control switch indicators will flash continuously to prompt the driver that service is required. The transfer case system will be disabled and the TCCM power relays will remain energized even with the ignition in the OFF position. This may cause the battery to discharge. Any other condition that sets a DTC 003 will not follow this routine but a fault code will be stored.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit .

Diagnostic Aids

When the vehicle is equipped with a manual transmission the clutch pedal must be depressed and working correctly in order for the transfer case to shift to the 4 low position. In order to confirm that it is operating correctly go the engine data 1 screen under the engine data display and observe the clutch pedal switch parameter.

Test Description

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

  1. This step tests the power control relays inside the TCCM.

    2.

  2. This step tests for voltage to the ATC/4WD fuse.

    3.

  3. This step tests the ATC/4WD fuse.

    4.

  4. This step tests for a voltage polarity change at the motor.

    5.

  5. This step tests for voltage at circuit 16 Battery Positive Voltage.

    6.

  6. This step tests for continuity to ground at circuit Ground.

    7.

  7. This step tests for continuity on motor control A and B circuits.

  8. This step tests for a grounded or shorted motor.

    9.

  9. This step tests for a short to ground on circuit 16 Battery Positive Voltage.

    10.

  10. This step tests for a short to ground on circuits Motor Control A and Motor Control B.

Step

Action

Value(s)

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following 4 steps to obtain DTCs.

  1. Turn OFF the ignition for 10 seconds.
  2. Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver side.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the transfer case shift control switch select buttons for flashing codes.

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Start the vehicle.
  2. Request a mode shift between 2HI and 4HI.
  3. Observe the transfer case shift control indicator lamps.

Are all of the lamps flashing together?

--

Go to Step 17

Go to Step 3

3

Test the voltage to the ATC fuse.

Does the test light illuminate?

--

Go to Step 4

Go to Step 15

4

  1. Remove the fuse.
  2. Observe the fuse element.

Is the fuse open?

--

Go to Step 9

Go to Step 5

5

  1. Disconnect the motor harness connector.
  2. Turn the ignition switch RUN with engine OFF.
  3. Put the transmission in Neutral.
  4. Connect a DMM between Motor Control A and Motor Control B circuits.
  5. Have a helper request changes by alternately pressing 4HI and 4LOW.

Does the polarity change according to the specified value?

+Battery Voltage/-Battery Voltage

Go to Step 16

Go to Step 6

6

  1. Turn the ignition switch to OFF.
  2. Disconnect the TCCM harness connector.
  3. Test for voltage at both of the Battery Positive Voltage circuits at the TCCM.

Did the test light illuminate on both tests?

--

Go to Step 7

Go to Step 12

7

Test for continuity to ground at the ground circuits at the TCCM.

Did you have continuity on both tests?

--

Go to Step 8

Go to Step 13

8

Test for continuity on Motor Control A and B circuits.

Did you have continuity on both tests?

--

Go to Step 17

Go to Step 14

9

  1. Turn the ignition switch to OFF.
  2. Disconnect the motor harness.
  3. Set the DMM for continuity.
  4. Connect the DMM to the body of the motor and pin 6 on the motor.
  5. Connect the DMM to the body of the motor and pin 7 on the motor.
  6. Connect the DMM across pins 6 and 7 at the motor.

Did you measure continuity, 0 Ohms, on any of the 3 tests?

--

Go to Step 16

Go to Step 10

10

    Important: Make sure you do not contact the positive side of the fuse terminal. Sending power to the DMM when checking continuity may damage the meter.

  1. Remove the harness connector from the TCCM.
  2. Remove the ATC fuse.
  3. Connect one lead of a DMM to a known ground and the other lead to the ground side of the ATC fuse terminal.

Do you have continuity?

--

Go to Step 12

Go to Step 11

11

  1. Disconnect the motor connector.
  2. Test for a short to ground on the Motor Control A and Motor Control B circuits.

Do you have continuity on either test?

--

Go to Step 14

Go to Step 17

12

Test the battery positive voltage circuit for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

13

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

Did you complete the repair?

--

Go to Step 18

--

14

Test Motor Control A or Motor Control B circuits for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

15

Repair the open circuit to the ATC fuse. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

16

Replace the transfer case encoder motor. Refer to Transfer Case Motor/Encoder Replacement .

Did you complete the repair?

--

Go to Step 18

--

17

Replace the TCCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the repair?

--

Go to Step 18

--

18

  1. Connect all of the connectors.
  2. Install a new ATC fuse.
  3. Clear all DTCs from memory. Refer to Diagnostic Trouble Code (DTC) Clearing .
  4. Operate the vehicle while requesting mode and range shifts.

Does the DTC reset?

--

Go to Step 01

System OK