GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Chevy P32 RV/Van Chassis 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Tachometer Inaccurate

Step

Action

Value(s)

Yes

No

1
  1. Start the engine.
  2. Observe the instrument cluster tachometer.
  3. Turn the engine OFF.

Did the instrument cluster tachometer operate?

--

Go to Step 10

Go to Step 2

2

Inspect the ECM 1 fuse in the instrument panel (IP) fuse block.

Is the fuse open?

--

Go to Step 3

Go to Step 4

3

Locate and repair the source of the overload in CKT 439 (PNK) between the IP fuse block and the instrument cluster connector.

Did you complete the repair?

--

System OK

--

4

Inspect the condition of G108.

Is G108 clean and tight?

--

Go to Step 6

Go to Step 5

5

Repair G108 as necessary.

Did you complete the repair?

--

System OK

--

6
  1. Disconnect the instrument cluster .
  2. Turn the ignition to the RUN position.
  3. Connect a test light from the instrument cluster connector, cavity 7 to ground. Refer to Using Connector Test Adapters in Wiring Systems.

Did the test light illuminate?

--

Go to Step 8

Go to Step 7

7

Locate and repair the open in CKT 439 (PNK) between the IP fuse block and the instrument cluster connector.

Did you complete the repair?

--

System OK

--

8

Connect a test light from the instrument cluster connector, cavity 4 to B+.

Did the test light illuminate?

--

Go to Step 10

Go to Step 9

9

Locate and repair the open in CKT 451 (BLK/WHT) between the instrument cluster connector and G108.

Did you complete the repair?

--

System OK

--

10
  1. Turn the ignition to the OFF position.
  2. Disconnect the ignition coil for gasoline engines, or the generator for diesel engines.
  3. Inspect CKT 121 (WHT) between the instrument cluster connector, cavity 6 and the ignition coil connector, cavity B (gasoline) , or the generator connector, cavity P (diesel) for the following conditions:
    4. • An open
    • Poor connections
    • Any indications of high resistance
    • A short to ground
    • A short to battery voltage

Did you find a condition?

--

Go to Step 11

Go to Step 12

11

Repair any condition found in CKT 121 (WHT).

Did you complete the repair?

--

System OK

--

12
  1. Connect the generator on diesel engines, or the ignition coil on gasoline engines.
  2. Start the engine.
  3. Use a J 39200 DMM in order to measure the voltage from the instrument cluster connector, cavity 6 to ground.
  4. Observe the J 39200 DMM for potentially pulsating voltage at or below 14 volts.
  5. Turn the engine OFF.

Was there voltage at cavity 6 of the instrument cluster connector?

--

Go to Step 13

Go to Step 15

13
  1. Start the engine.
  2. Install a Scan Tool .
  3. Select the Engine Speed display on the scan tool.
  4. Observe the engine speed displayed by the scan tool and the revolutions per minute (RPM) indicated by the instrument cluster tachometer.

Is the instrument cluster tachometer within specifications?

250 RPM

System OK

Go to Step 14

14

Replace the instrument cluster.

Did you complete the repair?

--

System OK

--

15
    • For diesel engines, replace the generator. Refer to Generator Replacement in Engine Electrical.
    •  For gasoline engines, replace the ignition coil on gasoline engines. Refer to Ignition Coil and Ignition Coil Module Replacement in Engine Electrical.

Did you complete the repair?

--

System OK

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