GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2007 🢒 H2 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 Fuel Gage Inaccurate or Inoperative

Diagnostic Aids
    • Verify that the fuel level is in the same range as the customer concern.
    • For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections .
    • Refer to Fuel Level Specifications in order to verify the correct readings for the fuel level sensor. The Fuel Tank Level Remaining parameter is available on the scan tool in the PCM Enhanced EVAP data list.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for a high resistance in the signal circuit and the low reference circuit of the fuel level sensor.

    2.

  2. DTCs will set in the powertrain control module (PCM) when you perform this diagnostic table.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Disconnect C106.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sensor and the low reference circuit of the fuel level sensor on the female terminal side of the connector.
  3. Turn the ignition ON, with the engine OFF.

    4. Important: Verify the J 33431-C resistance settings with a DMM.

  4. Vary the resistance on the J 33431-C from 40-250 ohms.
  5. Refer to Fuel Level Specifications in order to convert from resistance to fuel gage display.

Does the fuel gage display the correct fuel level?

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Go to Step 4

Go to Step 3

3

  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.

    3. Important: Verify the J 33431-C resistance settings with a DMM.

  3. Vary the resistance on the J 33431-C from 40-250 ohms.
  4. Refer to Fuel Level Specifications in order to convert from resistance to fuel level percentage.

    5. Important: Turn OFF the ignition momentarily between the resistance settings in order to quickly update the scan tool display.

  5. With the scan tool, observe the Fuel Tank Level Remaining parameter in the PCM Enhanced EVAP Data List.

Does the scan tool display the correct fuel level percentage?

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Go to Step 11

Go to Step 5

4

Inspect for the following items:

    • A poor connection at the harness connector of the fuel level sensor--Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .
    • A high resistance in the signal circuit of the fuel level sensor or the low reference circuit of the fuel level sensor between the fuel level sensor and C106.
    • A misaligned fuel level sender.
    • A deformed fuel tank.

Did you find and correct the condition?

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Go to Step 13

Go to Step 7

5

Test the signal circuit of the fuel level sensor for a high resistance. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 6

6

Test the low reference circuit of the fuel level sensor for a high resistance. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 9

7
  1. Remove the fuel level sender.
  2. Inspect for the following items:
    3. • The fuel level sensor is stuck, perhaps due to an interference with the fuel strainer.
    • The fuel tank contains foreign material, for instance, ice.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8
  1. With the J 39200 DMM, measure the resistance of the fuel level sensor while moving the float arm.
  2. Observe both the analog and digital displays on the DMM.

Does the resistance change smoothly across the specified range?

40-250 ohms

Go to Diagnostic Aids

Go to Step 10

9

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

10

Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement .

Did you complete the replacement?

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Go to Step 13

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11

Replace the instrument panel cluster (IPC). Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

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Go to Step 13

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12

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

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Go to Step 13

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13

  1. Use the scan tool in order to clear the PCM DTCs.
  2. Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2