GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Were you sent here from a diagnostic table?

Go to Step 2

Refer to Electric Shift Transfer Case Functional Test

2

  1. Check the 10 AMP Illumination fuse (number 5) in the IP fuse block for an open.
  2. Check the 10 AMP power fuse (number 15) in the IP fuse block for an open.
  3. Check the 20 Amp ATC fuse in the underhood bussed electrical center (UBEC) for an open.

Is one of the fuses open?

Go to Step 3

Refer to All Shift Select Buttons Remain Lit

3

  1. Replace the fuse.
  2. Turn the ignition switch to the RUN position.
  3. Check the operation of the electronic shift system.
  4. Check the fuse for an open.

Is the fuse open?

Go to Step 4

Refer to Electric Shift Transfer Case Functional Test

4

  1. Turn the ignition switch to the OFF position.
  2. Check pins C1 and C2 on the shift select switch for a ground if fuse 5 or 15 in the IP block was open.
  3. Check CKT 1640 for a ground if the ATC fuse was open.

Was one of the CKT grounded?

Go to Step 5

Go to Step 6

5

  1. Position the ignition switch to OFF.
  2. Repair the grounded CKT.
  3. Replace the fuse.

Is the repair completed?

Refer to Electric Shift Transfer Case Functional Test

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6

Check pin A on the back of the shift select switch for B+ voltage.

Is B+ voltage on pin A?

Go to Step 8

Go to Step 7

7

  1. Open wire in CKT 1220 between the fuse and pin C1, or CKT 241between the fuse and pin C2.
  2. Repair the open.
  3. Check for loose electrical connectors.

Is the repair complete?

Refer to Electric Shift Transfer Case Functional Test

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8

  1. Position the ignition switch to RUN.
  2. Do not unplug the harness connector from the shift select switch.
  3. Depress all three shift select buttons as the following pins are checked for B+ voltage.
  4. Check pins A, B, and F on the back of the shift select switch for B+ voltage.

Is B+ voltage at pin A, B, or F?

Go to Step 9

Go to Step 10

9

  1. Position the ignition switch to OFF.
  2. Ensure pin D10 on the TCCM is grounded.

Is pin D10 grounded?

Go to Step 12

Go to Step 11

10

  1. Position the ignition switch to OFF.
  2. Replace the shift select switch.

Has the shift select switch been replaced?

Refer to Electric Shift Transfer Case Functional Test

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11

  1. An open in CKT 1050 between pin D10 and ground.
  2. Repair the open in CKT 1050.

Is the repair completed?

Refer to Electric Shift Transfer Case Functional Test

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12

Check pins C6 and C8 on the TCCM for B+ voltage.

Is B+ voltage at pins C6 and C8?

Refer to Perform a Diagnostic On the TCCM

Go to Step 13

13

  1. If no B+ is on C6, an open exists on CKT 40 between the fuse and pin C6 on the TCCM.
  2. If no B+ is on C8, an open exist on CKT 241 between the fuse and pin C8 on the TCCM.

Is the open repaired?

Refer to Electric Shift Transfer Case Functional Test

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