DEFINITION: The Tachometer on the Instrument Cluster does not indicate engine RPM with the engine running. Alternatively, it may indicate RPM with the engine stopped or it may indicate an excessively high RPM. The engine operates without other ignition related symptoms.

1. Start the engine.
2. Vary the engine speed.
3. Observe the Tachometer indication on the Instrument Cluster.
4. Place the Ignition Switch in the Off position.

Does the Tachometer indicate a varying engine speed?

--

Go to Step 11

Go to Step 2

2

1. Disconnect the connector at the Ignition Coil.
2. Using an ohmmeter, measure the resistance between Ignition Coil connector Cavity B for the WHT (121) wire and ground.

Is the resistance to ground less than 1.2 ohms?

1.2 ohms

Go to Step 3

Go to Step 6

3

1. Disconnect the Instrument Cluster.
2. Using an ohmmeter, measure the resistance between Instrument Cluster Pins 8 and 11.

Is the resistance to ground less than 1.2 ohms?

1.2 ohms

Go to Step 5

Go to Step 4

4

1. Locate and repair the short to ground on the WHT (121) wire between the Ignition Coil and the Instrument Cluster.
2. Reconnect the Ignition Coil.
3. Reconnect the Instrument Cluster.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--

5

1. Replace the Instrument Cluster.
2. Reconnect the Ignition Coil.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--

6

1. Disconnect the Instrument Cluster.
2. Connect a self-powered test lamp between Instrument Cluster connector Cavity 8 and Ignition Coil connector Cavity B for the WHT (121) wire.

Does the test lamp light?

--

Go to Step 8

Go to Step 7

7

1. Locate and repair the open circuit in the WHT (121) wire between the Ignition Coil and the Instrument Cluster.
2. Reconnect the Instrument Cluster.
3. Reconnect the Ignition Coil.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--

8

1. Reconnect the Ignition Coil.
2. Reconnect the Instrument Cluster.
3. Connect a voltmeter between Instrument Cluster connector Cavity 8 for the WHT (121) wire and ground.
4. Start the engine.
5. Observe the voltage indication.
6. Place the Ignition Switch in the Off position.

Was signal voltage present on the WHT (121) wire?

--

Go to Step 9

Go to Step 10

9

Replace the Instrument Cluster.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--

10

Replace the Ignition Coil.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--

11

1. Connect a scan tool to the Data Link Connector.
2. Start the engine.
3. Monitor the engine speed with the scan tool.
4. Monitor the Tachometer indication on the Instrument Cluster.
5. Compare the two indications.

Is the Tachometer indication on the Instrument Cluster within 100 RPM of the actual value?

100 RPM

Go to Engine Electrical Diagnostic System Check .

Go to Step 12

12

Replace the Instrument Cluster.

Are the repairs complete?

--

Go to Engine Electrical Diagnostic System Check .

--