GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Fuel Gage Inaccurate or Inoperative

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 sensor ground circuit of the fuel level sender.

  1. DTCs will 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 IPC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Disconnect C405A/C405B.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sensor and the sensor ground 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 gage move from empty to full?

--

Go to Step 4

Go to Step 3

3

  1. Install a scan tool.
  2. Turn on the ignition, 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 Tank Level Remaining parameter in the PCM EVAP data list.

Does the Fuel Tank Level Remaining 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 sensor ground circuit between the fuel level sensor and C405A/C405B. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
    • A misaligned fuel level sensor
    • A deformed fuel tank

Did you find and correct the condition?

--

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 6

6

Test the sensor ground 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 sensor.
  2. Inspect for the following items:
    3. • A stuck fuel level sensor (i.e. the fuel strainer interfering with the sensor 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 in Engine Controls-3.8L or to Fuel Level Sensor Replacement in Engine Controls-5.7L.

Did you complete the replacement?

--

Go to Step 13

--

11

Important: Perform the setup procedure for the replacement IPC.

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/Programming in Engine Controls-3.8L or to Powertrain Control Module Replacement/Programming in Engine Controls-5.7L.

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