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.

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.

  2. DTCs will be set in the PCM when you perform this diagnostic table.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics or Engine Controls Schematics

1

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

  1. Disconnect C413 (fuel systems).
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit and the low reference circuit of the fuel level sensor (male terminal side).
  3. Turn the ignition ON, with the engine OFF.
  4. Important: Verify the J 33431-C resistance settings with a DMM.

  5. Vary the resistance on the J 33431-C from 40-250 ohms.

Does the fuel gage move from empty to full?

--

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.

  4. Vary the resistance on the J 33431-C from 40-250 ohms.
  5. Important: Turn the ignition OFF momentarily between the resistance settings in order to quickly update the scan tool display.

  6. With the scan tool, observe the Fuel Level parameter in the PCM EVAP data list.

Does the Fuel Level parameter move from approximately 0 % to approximately 100 %?

--

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 in Wiring Systems.
    • A high resistance in the signal circuit or the low reference circuit between the fuel level sensor and C413. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
    • A misaligned fuel level sender.
    • A deformed fuel tank.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 7

5

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

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 in Wiring Systems.

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. • A stuck fuel level sensor (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 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 PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

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 (2.4L) or to Fuel Level Sensor Replacement (3.4L) in Engine Controls.

Did you complete the replacement?

--

Go to Step 13

--

11

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

--

Go to Step 13

--

12

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls (2.4L) or to Powertrain Control Module Replacement/Programming (3.4L) in Engine Controls.

Did you complete the replacement?

--

Go to Step 13

--

13

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

Did you correct the condition?

--

System OK

Go to Step 2