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. Position the ignition switch to OFF for at least 6 seconds.
  2. Position the ignition switch to RUN.

Can any mode or range shifting be made?

Go to Step 3

Go to Step 8

3

Can shift modes (2H1 to 4H1 to 2H1) be made?

Go to Step 4

Go to Step 7

4

  1. Position the ignition switch to RUN.
  2. Check for B+ voltage at pins D2 and D16 on the TCCM.

Was B+ voltage on both pins?

Refer to Perform a Diagnostic On the TCCM

Go to Step 5

5

  1. Position the ignition switch to OFF.
  2. Check for an open between CKT 1737 and D16 on the TCCM.
  3. Check for an open between CKT 275 and D2 on the TCCM.

Was an open found on one of the CKT?

Go to Step 6

Refer to Perform a Diagnostic On the TCCM

6

  1. Ensure the ignition switch is positioned to OFF.
  2. Repair the open in the CKT.

Is the repair completed?

Refer to Electric Shift Transfer Case Functional Test

--

7

  1. Position the ignition switch to RUN.
  2. If 2H1 can not be selected, check for an open on CKT 1562 between pin C4 on the TCCM and Pin B on the shift select switch.
  3. If 4H1 can not be selected, check for an open on CKT 1564 between pin C5 on the TCCM and pin C on the shift select switch.

Was an open found on one of the CKT?

Go to Step 6

Refer to Perform a Diagnostic On the TCCM

8

  1. Position the ignition switch to RUN.
  2. Check for an open on CKT 1555 between pin D5 on the TCCM and pin C on the motor/encoder.

Was an open found on CKT 1555?

Go to Step 6

Refer to Perform a Diagnostic On the TCCM