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SMU - Revised Fuel Gage Inaccurate or Inoperative Diagnostic Procedure

Subject:Revised Fuel Gage Inaccurate or Inoperative Diagnostic Procedure

Models:1999-2000 Chevrolet Malibu
1999 Oldsmobile Cutlass


This bulletin is being revised to correct the diagnostic table, add model years and change the service category. Please discard Corporate Bulletin Number 01-06-04-023A (Section 6 -- Engine).

This bulletin is being issued to revise the Fuel Gage Inaccurate or Inoperative diagnostic procedure in the Instrument Panel, Gauges and Console sub-section of the Service Manual. Please replace the current information in the appropriate Service Manual with the following information.

The following information has been updated within SI2000. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

Diagnostic Aids
    • Ensure that the fuel level is in the same range as the customer concern.
    • For intermittent diagnosis, refer to Intermittents and Poor Connections Diagnosis 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 sensor ground circuit of the fuel level sender.

    2.

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

Step

Action

Value(s)

Yes

No

Schematic Reference: 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.

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

Does the fuel level indication move freely between empty and full?

--

Go to Step 4

Go to Step 3

3

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

  4. With the scan tool, observe the Fuel Level parameter in the PCM Engine IPC Data list.

Does the Fuel Level parameter vary between 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 Intermittents and Poor Connections Diagnosis 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 Testing for Continuity 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 Testing for Continuity 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 Testing for Continuity 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 Intermittents and Poor Connections Diagnosis 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 in Engine Controls.

Did you complete the replacement?

--

Go to Step 13

--

11

Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement.

Did you complete the replacement?

--

Go to Step 13

--

12

Important: Program the replacement PCM.

Replace the PCM. Refer to PCM Replacement/Programming 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