GM Service Manual Online
For 1990-2009 cars only

Refer to

Indicator Lamps


Object Number: 216522  Size: FS
Engine Controls Components
Information Sensors/Switches Description
Engine Data Sensors - A/C Refrig Press, TP, MAP, ECT, IAT
Fuel Injectors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
.

Circuit Description

The PCM controls the pulse frequency in relationship to engine RPM, and sends the information class II to the Instrument Cluster.

Diagnostic Aids

Refer to Instrument Cluster in Electrical Diagnosis for additional diagnostic information.

Check for the following conditions:

    • Poor connection at the PCM or instrument cluster. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs , and Wiring Repairs .
    • Damaged harness. Inspect the wiring harness for damage. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs , and Wiring Repairs .

Tachometer Control Circuit

Step

Action

Value(s)

Yes

No

1

Was Instrument Cluster diagnosis performed?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

Was the Powertrain On-Board Diagnostic System Check performed?

--

Go to Step 3

Go to Powertrain On Board Diagnostic (OBD) System Check

3

Are there any DTCs set?

--

Go to applicable DTCs

Go to Step 4

4

  1. Install scan tool.
  2. Start the engine.
  3. Observe the engine RPM on the scan tool.

Does the scan tool RPM match the Instrument Cluster?

--

System OK Refer to Diagnostic Aids

Go to Step 5

5

Verify proper operation of scan tool.

Connect scan tool to another vehicle and observe the RPM.

Does scan tool match vehicle RPM?

--

Go to Tachometer Inaccurate or Tachometer Inoperative

System OK Refer to Diagnostic Aids