GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

    • Ensure 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 in Wiring Systems.
    • Refer to Fuel Level Specifications in order to verify the correct fuel level sender readings. The Fuel Level (%) parameter is available on the scan tool in the PCM EVAP data list.

Test Description

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

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

Step

Action

Value(s)

Yes

No

1

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

  1. Disconnect the fuel level sender.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sender and the low reference circuit of the fuel level sender.
  3. Turn ON the ignition, with the engine OFF.
  4. Vary the resistance on the J 33431-C from 40-250 ohms. Refer to Fuel Level Specifications in order to convert from resistance to fuel gauge display.

Does the fuel gauge display the correct fuel level?

--

Go to Step 3

Go to Step 4

3

Inspect for the following items:

    • A poor connection at the harness connector of the fuel level sender. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    • A deformed fuel tank.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 6

4

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

Did you find and correct the condition?

--

Go to Step 11

Go to Step 5

5

Test the ground circuit of the fuel level sender for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

6

  1. Remove the fuel level sender.
  2. Inspect for the following items:
  3. • A stuck fuel level sender (i.e. the fuel strainer interfering with the sender float arm)
    • Foreign material in the gas tank (ice)

Did you find and correct the condition?

--

Go to Step 11

Go to Step 7

7

  1. With the DMM, measure the resistance of the fuel level sender 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 9

8

Inspect for poor connections at the harness connector of the instrument cluster. 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 11

Go to Step 10

9

Replace the fuel level sender. Refer to Fuel Level Sensor Replacement in Engine Controls - 3.8L.

Did you complete the replacement?

--

Go to Step 11

--

10

Replace the instrument panel cluster. Refer to Instrument Cluster Lens Replacement .

Did you complete the replacement?

--

Go to Step 11

--

11

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2