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GM_MASTER_DENNY
GM_MASTER_DENNY, GM and ASE Master Tech/Shop Foreman
Category: Chevy
Satisfied Customers: 178
Experience:  Over 15 years experience in automotive repair. GM Mark Of Excellence Winner for several years.
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1999 Blazer: My 4 wheel drive will not engage..lights flash..4x4

Resolved Question:

MyXXXXXwill not engage on my 1999 Blazer. The lights flash when switching to Auto 4x4, 4Hi and 4Low. I can hear a motor and the TCCM. There is a coroded wire on the TCCM. Pin 1 I belive.
Submitted: 8 years ago.
Category: Chevy
Expert:  GM_MASTER_DENNY replied 8 years ago.

Hello. I suggest further inspecting the TCCM and connector. The lights on the 4X4 switch flash when the transfer case cannot complete a shift. The incomplete shift could be caused from the encoder motor not functioning properly. The TCCM is what controls the shifting. If there is corrosion on one of the wires, that can cause a poor connection and skew the voltage or ground readings.

Disconnect the TCCM connector and check for any corrosion on the pins of the TCCM. If you see corrosion there,you will need a new TCCM. If only the wire to the TCCM is corroded,replace the corroded portion of the wire and put on a new terminal end. The terminal ends can be purchased at your local Chevy dealer.

After the repairs are made,test the 4X4 system operation. If it still has the flashing lights,follow this chart below.

 

Switch Indicator Lamps Flash Continuously
Object Number: 382173  Size: MF
Click here for detailed picture of above image.

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

Drive the vehicle in four wheel drive mode in order to determine if torque is being applied to the front wheels (the vehicle will display crow-hop or jerking during tight turns).

Is torque being applied to the front wheels?

--

Go to Step 3

Go to Step 7

3

  1. Turn the ignition ON, engine ON.
  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 12

Go to Step 4

4

  1. Disconnect the connector at the front axle switch.
  2. Connect a fused jumper wire between the front axle switch harness connector terminal A and B.
  3. Observe the Front Axle Switch status on the Scan Tool .

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

--

Go to Step 13

Go to Step 5

5

Connect a J 39200 Digital Multimeter DMM between the front axle switch harness connector terminal A and ground.

Is the voltage reading within the specified values?

9-14 V

Go to Step 6

Go to Step 11

6

  1. Disconnect connector C1 at the transfer case shift control module.
  2. Measure the resistance between the front axle switch harness connector terminal B and the transfer case shift control module harness connect C1 terminal E14.

Is the resistance reading within the specified values?

0-5 ?

Go to Step 12

Go to Step 15

7

  1. Turn the ignition ON, engine ON.
  2. Connect a Scan Tool in order to command the Front Axle Actuator ON.

Does the Front Axle Actuator turn ON?

--

Go to Step 12

Go to Step 8

8

Inspect the front drive axle clutch solenoid for proper vacuum supply.

Is there proper vacuum supplied to the front drive axle clutch solenoid?

--

Go to Step 9

Go to Step 17

9

  1. Turn the ignition OFF.
  2. Disconnect connector C1 at the transfer case shift control module.
  3. Turn the ignition ON, engine ON.
  4. Use a fused jumper wire in order to ground the transfer case shift control module connector C1 terminal F4.

Does the front drive axle clutch solenoid engage the front axle?

--

Go to Step 12

Go to Step 10

10

  1. Disconnect the connector at the front drive axle clutch solenoid.
  2. Connect a J 39200 DMM and measure the voltage between the front drive axle clutch solenoid harness connector terminal A and ground.

Is the voltage within the values specified?

9-14 V

Go to Step 14

Go to Step 11

11

Repair an open in CKT 241. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 19

--

12

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

Is the repair complete?

--

Go to Step 19

--

13

Replace the front axle switch. Refer to front axle switch replacement.

Is the repair complete?

--

Go to Step 19

--

14

Connect a J 39200 DMM and measure the resistance between the front drive axle clutch solenoid harness connector terminal B and the transfer case shift control module harness connector C1 terminal F4.

Is the resistance within the values specified?

0-5?

Go to Step 18

Go to Step 16

15

Repair an open in CKT 1695. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 19

--

16

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

Is the repair complete?

--

Go to Step 19

--

17

Repair a vacuum leak between the engine and the front drive axle clutch solenoid.

Is the repair complete?

--

Go to Step 19

--

18

Replace the front drive axle clutch solenoid. Refer to front drive axle clutch solenoid replacement.

Is the repair complete?

--

Go to Step 19

--

19

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 20

--

20

Clear all the ATC DTCs.

Are all the ATC DTCs been cleared?

--

Go to Transfer Case Diagnostic System Check

--

GM_MASTER_DENNY and other Chevy Specialists are ready to help you
Expert:  GM_MASTER_DENNY replied 8 years ago.

Hello. I suggest further inspecting the TCCM and connector. The lights on the 4X4 switch flash when the transfer case cannot complete a shift. The incomplete shift could be caused from the encoder motor not functioning properly. The TCCM is what controls the shifting. If there is corrosion on one of the wires, that can cause a poor connection and skew the voltage or ground readings.

Disconnect the TCCM connector and check for any corrosion on the pins of the TCCM. If you see corrosion there,you will need a new TCCM. If only the wire to the TCCM is corroded,replace the corroded portion of the wire and put on a new terminal end. The terminal ends can be purchased at your local Chevy dealer.

After the repairs are made,test the 4X4 system operation. If it still has the flashing lights,follow this chart below.

 

Switch Indicator Lamps Flash Continuously
Object Number: 382173  Size: MF
Click here for detailed picture of above image.

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

Drive the vehicle in four wheel drive mode in order to determine if torque is being applied to the front wheels (the vehicle will display crow-hop or jerking during tight turns).

Is torque being applied to the front wheels?

--

Go to Step 3

Go to Step 7

3

  1. Turn the ignition ON, engine ON.
  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 12

Go to Step 4

4

  1. Disconnect the connector at the front axle switch.
  2. Connect a fused jumper wire between the front axle switch harness connector terminal A and B.
  3. Observe the Front Axle Switch status on the Scan Tool .

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

--

Go to Step 13

Go to Step 5

5

Connect a J 39200 Digital Multimeter DMM between the front axle switch harness connector terminal A and ground.

Is the voltage reading within the specified values?

9-14 V

Go to Step 6

Go to Step 11

6

  1. Disconnect connector C1 at the transfer case shift control module.
  2. Measure the resistance between the front axle switch harness connector terminal B and the transfer case shift control module harness connect C1 terminal E14.

Is the resistance reading within the specified values?

0-5 ?

Go to Step 12

Go to Step 15

7

  1. Turn the ignition ON, engine ON.
  2. Connect a Scan Tool in order to command the Front Axle Actuator ON.

Does the Front Axle Actuator turn ON?

--

Go to Step 12

Go to Step 8

8

Inspect the front drive axle clutch solenoid for proper vacuum supply.

Is there proper vacuum supplied to the front drive axle clutch solenoid?

--

Go to Step 9

Go to Step 17

9

  1. Turn the ignition OFF.
  2. Disconnect connector C1 at the transfer case shift control module.
  3. Turn the ignition ON, engine ON.
  4. Use a fused jumper wire in order to ground the transfer case shift control module connector C1 terminal F4.

Does the front drive axle clutch solenoid engage the front axle?

--

Go to Step 12

Go to Step 10

10

  1. Disconnect the connector at the front drive axle clutch solenoid.
  2. Connect a J 39200 DMM and measure the voltage between the front drive axle clutch solenoid harness connector terminal A and ground.

Is the voltage within the values specified?

9-14 V

Go to Step 14

Go to Step 11

11

Repair an open in CKT 241. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 19

--

12

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

Is the repair complete?

--

Go to Step 19

--

13

Replace the front axle switch. Refer to front axle switch replacement.

Is the repair complete?

--

Go to Step 19

--

14

Connect a J 39200 DMM and measure the resistance between the front drive axle clutch solenoid harness connector terminal B and the transfer case shift control module harness connector C1 terminal F4.

Is the resistance within the values specified?

0-5?

Go to Step 18

Go to Step 16

15

Repair an open in CKT 1695. Refer to Wiring Repairs in wiring systems.

Is the repair complete?

--

Go to Step 19

--

16

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

Is the repair complete?

--

Go to Step 19

--

17

Repair a vacuum leak between the engine and the front drive axle clutch solenoid.

Is the repair complete?

--

Go to Step 19

--

18

Replace the front drive axle clutch solenoid. Refer to front drive axle clutch solenoid replacement.

Is the repair complete?

--

Go to Step 19

--

19

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 20

--

20

Clear all the ATC DTCs.

Are all the ATC DTCs been cleared?

--

Go to Transfer Case Diagnostic System Check

--

GM_MASTER_DENNY and other Chevy Specialists are ready to help you

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