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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Body and Accessories 🢒 Instrument Panel, Gages, and Console 🢒 Fuel Gage Inaccurate or Inoperative

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 in Wiring Systems.
    • 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 (%) 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 PCM when you perform this diagnostic table.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster 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 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 4

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 %.

    5. Important: Turn OFF the ignition 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 Engine Data Fuel System display-6.6L diesel only

Does the scan tool display the correct fuel level %?

--

Go to Step 11

Go to Step 5

4

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 in Wiring Systems.
    • 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 13

Go to Step 7

5

Test the signal circuits of the fuel level senders for a high resistance between C152 and the PCM. 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 senders for a high resistance between C152 and the PCM. 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 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, 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 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 10

9

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

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

10

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

    •  Fuel Level Sensor Replacement in Engine Controls - 4.3L
    •  Fuel Level Sensor Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L
    •  Fuel Level Sensor Replacement in Engine Controls - 6.6L
    •  Fuel Level Sensor Replacement in Engine Controls - 8.1L

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 the following procedures:

    •  Powertrain Control Module Replacement in Engine Controls - 4.3L
    •  Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L
    •  Engine Control Module Replacement in Engine Controls - 6.6L
    •  Powertrain Control Module Replacement in Engine Controls - 8.1L

Did you complete the replacement?

--

Go to Step 13

--

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

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 in Wiring Systems.
    • 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 the Fuel Level Sensor (%) parameter in the Engine Data Fuel System display (6.6 L diesel only).

Test Description

The number below refer to the step number 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

Value(s)

Yes

No

Schematic Reference: Instrument Cluster 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 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 ON the ignition, 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 4

Go to Step 3

3

  1. Install the scan tool.
  2. Turn ON the ignition, 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 %.

    5. Important: Turn OFF the ignition 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 Engine Data Fuel System display (6.6 L diesel only)

Does the scan tool display the correct fuel level %?

--

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 sender
        Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    • 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 13

Go to Step 7

5

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 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 sender for a high resistance between C152 and the PCM. 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, i.e. 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 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 10

9

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and 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 sender. Refer to the following procedures:

    •  Fuel Level Sensor Replacement in Engine Controls-4.3L
    •  Fuel Level Sensor Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L
    •  Fuel Level Sensor Replacement in Engine Controls - 6.6L
    •  Fuel Level Sensor Replacement in Engine Controls - 8.1L

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 - 4.3L
    •  Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L
    •  Engine Control Module Replacement in Engine Controls - 6.6L
    •  Powertrain Control Module Replacement in Engine Controls - 8.1L

Did you complete the replacement?

--

Go to Step 13

--

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