GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Jimmy - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Voltmeter Displaying High or Low

Step

Action

Value(s)

Yes

No

1

Did you perform the Starting System Check?

--

Go to Step 2

Go to Starting System Check

2
  1. Turn all of the electrical loads OFF.
  2. Start the engine.
  3. Briefly idle the engine.
  4. Use a scan tool in order to inspect the charging voltage.

Is the voltage within the specified range?

13-16 V

Go to Step 3

Go to Step 6

3

Compare the scan tool reading with a reading obtained at the same time (engine at idle) from the vehicle voltmeter.

Is the difference between the vehicle voltmeter reading and the scan tool reading within the specified range?

2 V

Go to Step 4

Go to Step 7

4
  1. Increase the engine speed to 2500 RPM.
  2. Use a scan tool in order to inspect the charging voltage.

Is the voltage within the specified range?

13-16 V

Go to Step 5

Go to Step 6

5

Compare the scan tool reading with a reading obtained at the same time (engine at 2500 RPM) from the vehicle voltmeter.

Is the difference between the vehicle voltmeter reading and the scan tool reading within the specified range?

2 V

Go to Starting System Check

Go to Step 7

6

Perform the Charging System Check .

Is the generator OK?

--

Go to Step 11

Go to Step 12

7

Inspect the instrument cluster for an incorrect voltmeter reading condition.

Is the instrument cluster operating properly?

--

Go to Step 9

Go to Step 8

8

Repair the instrument cluster as necessary.

Is the repair complete?

--

Go to Starting System Check

--

9

Inspect the PCM or the VCM for an incorrect voltmeter reading condition.

Is the PCM or VCM operating properly?

--

Go to Step 11

Go to Step 10

10

Repair the PCM or the VCM as necessary.

Is the repair complete?

--

Go to Starting System Check

--

11
  1. Disconnect the battery negative cable.
  2. Disconnect and clean all of the connections between the battery positive terminal and the generator output terminal.
  3. Disconnect and clean all of the connections in the ground circuit between the battery negative terminal and the generator housing.
  4. Inspect all of the cables for an intermittent open condition.
  5. Connect the battery negative cable.

Is the repair complete?

--

Go to Starting System Check

--

12

Replace the generator. Refer to Generator Replacement .

Is the repair complete?

--

Go to Starting System Check

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