GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Blazer - 2WD 🢒 DTC 🢒 DTC C0309 Motor A/B Circuit High

Object Number: 234899 Size: MF
Power Sheet 2: W/ Automatic 4WD
Handling Electrostatic Discharge Sensitive Parts Notice
Engine Electrical Components
Cell 38: Transfer Case Vehicle Speed Sensors

Circuit Description

The transfer case encoder motor is a permanent magnet D.C. motor and gear reduction assembly. The encoder motor is controlled with a Pulse Width Modulated (PWM) circuit within the transfer case shift control module. This circuit consists of a power supply relay (Motor A) circuit that supplies voltage to the motor through CKT 1552. The Motor B circuit (CKT 1553) is a PWM driver that varies the duty cycle to control the amount of current through the motor to ground.

This DTC detects a short to power on circuits 1552 and 1553.

Conditions for Setting the DTC
  1. The system will test the motor circuits by checking for unwanted voltage.
  2. The system supplies voltage on the Motor A circuit and reads the voltage back on the Motor B circuit.
  3. The transfer case shift control module senses a high voltage return on circuits 1552 or 1553 when a low voltage is expected.
  4. If the system detects a problem with the circuits, the DTC is logged.

Action Taken When the DTC Sets
    • All clutch activation (slip control) will be disabled.
    • The SERVICE AWD/4WD lamp will be latched on for the remainder of the current ignition cycle.

Conditions for Clearing the MIL/DTC
    • Current DTC
        The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
    • History DTC
       - Once 100 consecutive ignition cycles without a fault present.
       - You issue a scan tool CLEAR CODES command.

DTC C0309 Motor A/B Circuit High

Step

Action

Value(s)

Yes

No

1

Was the Transfer Case Diagnostic System Check performed?

--

Go to Step 2

Go to Transfer Case Diagnostic System Check

2
  1. Turn the ignition OFF.
  2. Disconnect both transfer case shift control module connectors.
  3. Connect a J 39200 Digital Multimeter between the shift control module connector C2 terminal A and ground.
  4. Turn the ignition to RUN.

Is the voltage reading greater than the specified value?

0 V

Go to Step 3

Go to Step 5

3
  1. Turn the ignition OFF.
  2. Disconnect the transfer case encoder motor.
  3. Connect the J 39200 between the shift control module connector C2 terminals A and ground.
  4. Turn the ignition to RUN.

Is the voltage reading greater than the specified value?

0 V

Go to Step 4

Go to Step 6

4

Repair a short to voltage in CKT 1552.

Is the repair complete?

--

Go to Step 7

--

5

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

Is the repair complete?

--

Go to Step 7

--

6

Repair a short to voltage in CKT 1553.

Is the repair complete?

--

Go to Step 7

--

7
  1. Ensure the ignition is OFF.
  2. Reconnect all previously disconnected components.

Are all the ATC components connected and properly mounted?

--

Go to Step 8

--

8

Clear all ATC codes.

Are all the ATC codes cleared?

--

Go to Transfer Case Diagnostic System Check

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