GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Tachometer Inaccurate or Inoperative

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for a malfunctioning component that is interrupting the RPM signal output circuit.

    2.

  2. This step tests for the proper voltage from the IPC.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Install a scan tool.
  2. Raise the vehicle's drive wheels. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Start the engine.
  4. Place the transmission into drive.
  5. With the scan tool, observe the Engine Speed parameter in the IPC data list.

Does the Engine Speed parameter match the speedometer display?

--

Go to Step 3

Go to Step 4

3

Does the odometer operate properly?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 12

4

  1. Turn the ignition OFF.
  2. Disconnect the HVAC module.
  3. Start the engine.
  4. Place the transmission into drive.
  5. With the scan tool, observe the Engine Speed parameter.

Does the Engine Speed parameter match the speedometer display?

--

Go to Step 8

Go to Step 5

5

  1. Turn the ignition OFF.
  2. Disconnect the ECM connector C2.
  3. Turn the ignition ON, with the engine OFF.
  4. Measure the voltage from the RPM signal output circuit to a good ground.

Does the voltage measure greater than the specified value?

9.0 V

Go to Step 7

Go to Step 6

6

Test the RPM signal output circuit for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

7

Test the RPM signal output circuit for a short to battery voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

8

Inspect for poor connections at the harness connector of the HVAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

9

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

10

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

11

Replace the HVAC control module. Refer to HVAC Control Module Replacement in HVAC Systems.

Did you complete the replacement?

--

Go to Step 14

--

12

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

--

Go to Step 14

--

13

Important: Program the replacement ECM.

Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2