GM Service Manual Online
For 1990-2009 cars only

Object Number: 380640  Size: MF
Transfer Case Control Components
Transfer Case Control Schematics

Range/Mode Selector Lamp Flashes Continuously (One or More)

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 ON, engine OFF.
  2. Connect a Scan Tool in order to determine Front Axle Switch status.

Does the Front Axle Switch status show the front axle Locked?

--

Go to Step 6

Go to Step 3

3

Continue to use the Scan Tool in order to determine if the transfer case is in Auto 4WD, 4WD HI or 4WD Low mode.

Is the transfer case in Auto 4WD, 4WD HI or 4WD Low mode?

--

Go to Step 4

Go to Step 13

4

  1. Disconnect the connectors at the transfer case shift control module.
  2. Turn the ignition ON, engine OFF.
  3. Measure the voltage between the transfer case shift control module connector C1 terminal E14 and ground.

Is the voltage within the specified values?

9-14 V

Go to Step 13

Go to Step 5

5

Connect a J 39200 Digital Multimeter DMM between the transfer case shift control module harness connector C1 terminal F4 and the front axle actuator terminal B .

Is the resistance reading within the specified values?

0-2 ohms

Go to Step 14

Go to Step 11

6

Continue to use the Scan Tool in order to determine if the transfer case is in 2WD mode.

Is the transfer case in 2WD mode?

0-2 ohms

Go to Step 7

Go to Step 13

7

  1. Disconnect connectors at the transfer case shift control module.
  2. Measure the voltage between the transfer case shift control module harness connector C1 terminal E14 and ground.

Is the voltage reading within the specified value?

0 V

Go to Step 13

Go to Step 8

8

  1. Disconnect the Front Axle Actuator connector.
  2. Measure the voltage between the Front Axle Actuator harness connector terminal A and Ground.

Is the voltage reading within the specified value?

0 V

Go to Step 9

Go to Step 12

9

Inspect the front axle to determine if the front axle is mechanically applied.

Is the front axle mechanically applied?

--

Go to Step 10

Go to Step 14

10

Service the front axle for a mechanical failure.

Is the repairs complete?

--

Go to Step 16

--

11

Repair an open in CKT 1570. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 16

--

12

Repair a short to voltage in CKT 1695. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 16

--

13

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

Is the repair complete?

--

Go to Step 16

--

14

Replace the Front Axle Actuator. Refer to Front Axle Actuator replacement.

Is the repair complete?

--

Go to Step 16

--

15

Replace the front drive axle clutch solenoid. Refer to Electric Motor Actuator Replacement .

Is the repair complete?

--

Go to Step 16

--

16

Reconnect all ATC system components, make sure all the components are properly mounted.

Have all the ATC components been reconnected and properly mounted?

--

Go to Step 17

--

17

Clear all the ATC DTCs.

Are all the ATC DTCs been cleared?

--

Go to Transfer Case Diagnostic System Check

--