GM Service Manual Online
For 1990-2009 cars only

Tachometer Inoperative Gas

Step

Action

Value(s)

Yes

No

1

Did you perform the OBD II System Check been performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check (5.0L/5.7L); Powertrain On Board Diagnostic (OBD) System Check (7.4L)

2

  1. Remove the I/P Cluster.
  2. Disconnect the Ignition Coil connector.
  3. Connect a J 39200 DMM (continuity) between I/P Cluster connector cavity 6 and ground.

Is continuity present?

--

Go to Step 3

Go to Step 4

3

Locate and repair the short to ground in CKT 121 (WHT) between the Ignition Coil and the I/P cluster. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Refer to Instrument Cluster System Check

--

4

Connect a J 39200 DMM (continuity) from I/P Cluster cavity 6 to ignition coil connector cavity B.

Is continuity present?

--

Go to Step 5

Go to Step 6

5

Replace the I/P Cluster. Refer to Instrument Cluster Replacement .

Is the repair complete?

--

Refer to Instrument Cluster System Check

--

6

Locate and repair the open in CKT 121 (WHT) between the Ignition Coil and the I/P Cluster. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Refer to Instrument Cluster System Check

--

Tachometer Inoperative Diesel

Step

Action

Value(s)

Yes

No

1

Did you perform the Instrument Cluster System Check?

--

Go to Step 2

Go to Instrument Cluster System Check

2

  1. Disconnect the connector at the instrument cluster.
  2. Disconnect the connector at the generator.
  3. Connect a test lamp between generator connector cavity A and ground.

Did the test lamp light?

--

Go to Step 3

Go to Step 4

3

Locate and repair the short to ground in CKT 121 (WHT) between the generator and the instrument cluster. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Instrument Cluster System Check

Go to Step 4

4

Connect a test lamp between instrument cluster connector cavity 6 and generator connector cavity A.

Did the test lamp light?

--

Go to Step 5

Go to Step 6

5

  1. Connect the connector at the generator.
  2. Start the engine.
  3. Connect a voltmeter or oscilloscope between instrument cluster connector cavity 6 and ground.
  4. Look for potentially pulsating voltage at or below 14 volts.

Is there voltage present?

14 V

Go to Step 7

Go to Step 8

6

Locate and repair the open in CKT 121 (WHT) between the generator and the instrument cluster. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Instrument Cluster System Check

--

7

Replace the instrument cluster. Refer to Instrument Cluster Replacement .

Is the repair complete?

--

Go to Instrument Cluster System Check

--

8

Replace the generator. Refer to Generator Replacement , Generator Replacement (CS 130D), or Generator Replacement - Auxiliary in Engine Electrical.

Is the repair complete?

--

Go to Instrument Cluster System Check

--