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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 Fuel Gage Inaccurate or Inoperative

Fuel Gage Inaccurate or Inoperative Single Tank

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 .
    • Refer to Fuel Level Specifications in order to verify the correct fuel level sender readings. The fuel level is available on the scan tool in the Fuel Tank Level Remaining (%) parameter in the powertrain control module (PCM) Enhanced EVAP Data list (gas only) or the Fuel Level Sensor (voltage) parameter in the Engine Data Fuel System display (6.6L diesel only).

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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

    2.

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

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Disconnect C152.
  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 (male terminal side).
  3. Turn the ignition ON, with the engine OFF.
  4. Vary the resistance on the J 33431-C from 40-250 ohms.

    5. Important: Verify the J 33431-C resistance settings with a DMM.

  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 5

Go to Step 3

3

  1. Install the scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Vary the resistance on the J 33431-C from 40-250 ohms.

    4. Important: Verify the J 33431-C resistance settings with a DMM.

  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 powertrain control module (PCM) Enhanced EVAP Data list - gas only
    • Fuel Level Sensor parameter in the PCM Fuel System data list - 6.6L diesel only

Does the scan tool display the correct fuel level percent?

--

Go to Step 4

Go to Step 6

4

With the scan tool, perform the Displays Test in the instrument panel cluster (IPC) scan tool Output Controls.

Does the gage move from 0 to its maximum value and back to 0 when you perform the Displays Test?

--

Go to Step 5

Go to Step 10

5

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 .
    • A high resistance in the signal circuit or the low reference circuit between the fuel level sender and C152
    • A misaligned fuel level sender
    • A deformed fuel tank

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

6

Test the signal circuit of the fuel level sender for a high resistance between C152 and the PCM. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 7

7

Test the low reference circuit of the fuel level sender for a high resistance between C152 and the PCM. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

8
  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, i.e. ice

Did you find and correct the condition?

--

Go to Step 15

Go to Step 9

9
  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 12

10

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

11

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

12

Replace the fuel level sender. Refer to the following procedures:

    •  Fuel Level Sensor Replacement for the 4.3L engine
    •  Fuel Level Sensor Replacement for the 4.8L, 5.3L, and 6.0L engines
    •  Fuel Level Sensor Replacement for the 6.6L (LBZ and LLY) engine
    •  Fuel Level Sensor Replacement for the 8.1L engine

Did you complete the replacement?

--

Go to Step 15

--

13

Replace the IPC. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

15

  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

Fuel Gage Inaccurate or Inoperative Dual Tanks

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 .
    • Refer to Fuel Level Specifications in order to verify the correct fuel level sender readings. The fuel level is available on the scan tool in the Fuel Tank Level Remaining (%) parameter in the PCM Enhanced EVAP Data list-gas only or in the Fuel Level Sensor (voltage) parameter in the Engine Data Fuel System display - 6.6L diesel only.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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

    2.

  2. DTCs will be set in the powertrain control module (PCM) when you perform this diagnostic table.

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Disconnect C152.
  2. Connect a jumper wire between the signal circuit of the primary fuel level sender and the signal circuit of the secondary fuel level sender-male terminal side.
  3. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuits of the fuel level senders and the low reference circuit of the fuel level senders-male terminal side.
  4. Turn ON the ignition, with the engine OFF.
  5. Vary the resistance on the J 33431-C from 40-250 ohms.

    6. Important: Verify the J 33431-C resistance settings with a DMM.

  6. 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 5

Go to Step 3

3

  1. Install the 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. Refer to Fuel Level Specifications in order to convert from resistance to fuel level percentage.

    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 list-gas only
    • Fuel Level Sensor parameter in the PCM Fuel System data list - 6.6L diesel only

Does the scan tool display the correct fuel level percentage?

--

Go to Step 4

Go to Step 6

4

With the scan tool, perform the Displays Test in the instrument panel cluster (IPC) scan tool Output Controls.

Does the gage move from 0 to its maximum value and back to 0 when you perform the Displays Test?

--

Go to Step 5

Go to Step 10

5

Inspect for the following items:

    • A poor connection at the harness connectors of the fuel level senders--Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
    • A high resistance in the signal circuits or the low reference circuit between the fuel level senders and C152
    • A misaligned primary or secondary fuel level sender
    • A deformed primary or secondary fuel tank

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

6

Test the signal circuits of the fuel level senders for a high resistance between C152 and the powertrain control module (PCM). Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 7

7

Test the low reference circuit of the fuel level senders for a high resistance between C152 and the PCM. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

8
  1. Remove the fuel level senders.
  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 tanks, i.e. ice

Did you find and correct the condition?

--

Go to Step 15

Go to Step 9

9
  1. With the DMM, measure the resistance of the fuel level senders 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 12

10

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

11

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

12

Replace the primary or the secondary fuel level sender. Refer to the following procedures:

    •  Fuel Level Sensor Replacement for the 4.3L engine
    •  Fuel Level Sensor Replacement for the 4.8L, 5.3L, and 6.0L engines
    •  Fuel Level Sensor Replacement for the 6.6L (LBZ and LLY) engine
    •  Fuel Level Sensor Replacement for the 8.1L engine

Did you complete the replacement?

--

Go to Step 15

--

13

Replace the instrument panel cluster (IPC). Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

15

  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