GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 TrailBlazer - 4WD 🢒 Body and Accessories 🢒 Instrument Panel, Gages, 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.
    • Refer to Fuel Level Specifications in order to verify the correct fuel level sensor readings. The Fuel Level (%) parameter is available on the scan tool in the powertrain control module (PCM) 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 be set in the PCM when you perform this diagnostic table.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Disconnect C101.
  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 male 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?

--

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 percent.

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

  5. With the scan tool, observe one of the following Fuel Level parameters:
    6. • Fuel Tank Level Remaining parameter in the PCM Enhanced EVAP Data data list.
    • Fuel Level Sensor parameter in the PCM EVAP Data data list - 4.2L only.

Does the scan tool indicate that the Fuel Tank Level Remaining or the Fuel Level Sensor parameter is less than the specified value?

--

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 in Wiring Systems.
    • 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 C101.
    • 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 signal circuit of the fuel level sensor for a high resistance. Refer to Circuit Testing and 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 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 sender (i.e. the fuel strainer interfering with the sender float arm).
    • Foreign material in the fuel tank (ice).

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8
  1. With the 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 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 - 4.2L or to Fuel Level Sensor Replacement in Engine Controls - 4.8L, 5.3L, or 6.0L.

Did you complete the replacement?

--

Go to Step 13

--

11

Important: Program the replacement instrument panel control (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 in Engine Controls - 4.2L or to Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, or 6.0L.

Did you complete the replacement?

--

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?

--

System OK

Go to Step 2