Step
| Action
| Value(s)
| Yes
| No
|
1
| Did you perform the Instrument Cluster Diagnostic System Check?
| --
|
Go to Step 2
| Go to
Diagnostic System Check - Instrument Cluster
|
2
| Verify that
the tachometer is inaccurate.
Does the tachometer operate normally?
| --
| Go to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems
| Go to
Step 3
|
3
|
- With a scan tool select Powertrain, Data Display, Engine Data
Display, and Data in order to monitor the engine speed.
- Start the engine.
- Compare the engine speed on the scan tool to the engine speed
displayed on the tachometer.
Does the scan tool agree with the tachometer?
| --
| Go to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems
| Go to
Step 4
|
4
|
- Test the tachometer signal circuit at the instrument cluster connector
by backprobing with a J 39200
digital multimeter (DMM). Refer to
Instrument Cluster Replacement
.
- Select the AC Voltage scale, then select frequency
- Measure the frequency between the tachometer signal circuit and
a good ground with the engine idling. Refer to
Circuit Testing
in Wiring Systems.
Does the frequency measure within the specified range?
| 15-25 HZ Engine Idling
|
Go to Step 5
|
Go to Step 6
|
5
| Replace the
instrument cluster. Refer to
Instrument Cluster Replacement
Did you complete the replacement?
| |
Go to Step 8
| --
|
6
| Test the
tachometer signal circuit for the following conditions:
| • | An open or a poor connection between the instrument cluster and
the vehicle control module (VCM) |
| • | A short to ground between the instrument cluster and the VCM |
| • | A short to battery voltage between the instrument cluster and
the VCM |
Did you find and correct the condition?
| --
|
Go to Step 8
|
Go to Step
7
|
7
| Replace the VCM. Refer to
VCM Replacement/Programming
in Engine Controls-4.3L.
Did you complete the replacement?
| --
|
Go to Step
8
| --
|
8
| Operate the system in order to verify the repair.
Did you correct the condition?
| --
| System OK
|
Go to Step
3
|
