Fuel Gage Inaccurate or Inoperative. Chevrolet Chevy C Cab/Chassis HD (GMT 400) 2005

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Body 🢒 Instrument Panel, Gages, and Console 🢒 Fuel Gage Inaccurate or Inoperative

Fuel Gage Inaccurate or Inoperative Single Tank 8.1L Gasoline Engine

Diagnostic Aids

•	Verify 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.

•

The Fuel Tank Level Remaining parameter is available on the scan tool in the PCM Enhanced EVAP Data data list. Use the fuel level sensor resistance to verify the fuel level sensor operation. When the fuel tank is empty, the fuel level sensor resistance is approximately 40 ohms. When the fuel tank is full, the fuel level sensor resistance is approximately 250 ohms.

Test Description

The number below refers to the step number on the diagnostic table.

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

Step

Action

Value(s)

Yes

Schematic Reference: Instrument Cluster Schematics

Did you perform the Instrument Cluster Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Disconnect C130.
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, on the female terminal side.
Turn the ignition ON, with the engine OFF.

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

Vary the resistance on the J 33431-C from 40-250 ohms.
Observe the fuel gage in the IPC.

Does the fuel gage move from approximately empty to approximately full?

Go to Step 4

Go to Step 3

Turn the ignition OFF.
Install a scan tool.
Turn the ignition ON, with the engine OFF.

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

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

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

With the scan tool, observe the Fuel Tank Level Remaining parameter in the PCM Enhanced EVAP Data data list.

Does the Fuel Tank Level Remaining parameter move from 0-98 %?

Go to Step 5

Go to Step 7

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 low reference circuit between the fuel level sensor and C130

Refer to Circuit Testing 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 16

Go to Step 9

Turn the ignition OFF.
Disconnect C2 of the PCM.
Connect the J 33431-C between the fuel level signal circuit and a good ground.
Turn the ignition ON, with the engine OFF.

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

Vary the resistance on the J 33431-C from 0-90 ohms.
Observe the fuel gage in the IPC.

Does the fuel gage move from empty to full?

Go to Step 12

Go to Step 6

Test the fuel level signal circuit 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 16

Go to Step 11

Test the signal circuit of the fuel level sensor for a high resistance between C130 and the PCM. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 8

Test the low reference circuit of the fuel level sensor for a high resistance between C130 and the PCM. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 12

Remove the fuel level sender.
Inspect for the following items:

•	The fuel level sensor is stuck, perhaps due to an interference with the fuel strainer.

•	The fuel tank contains foreign material, for instance ice.

Did you find and correct the condition?

Go to Step 16

Go to Step 10

With the J 39200 DMM, measure the resistance of the fuel level sensor while moving the float arm.
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 13

Inspect for poor connections at the harness connector of the IPC. 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 16

Go to Step 14

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 16

Go to Step 15

Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

Go to Step 16

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 16

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

Go to Step 16

Use the scan tool in order to clear the PCM DTCs.
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 Tank 8.1L Gasoline Engine

Diagnostic Aids

•	Verify 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 .

•	Use the fuel level sensor resistance to verify the fuel level sensor operation. When the fuel tank is empty, the fuel level sensor resistance is approximately 40 ohms. When the fuel tank is full the fuel level sensor resistance is approximately 250 ohms.

Test Description

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

This step tests for a malfunction in the fuel level sensor.

This step tests for a malfunction in the fuel level sensor signal circuit of the fuel balance module.

This step tests for a malfunction in the fuel level sensor signal circuit of the PCM.

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

Step

Action

Value(s)

Yes

Schematic Reference: Instrument Cluster Schematics

Did you perform the Instrument Cluster Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Disconnect the primary and the secondary fuel level sensors.
Connect a jumper wire between the signal circuit of the primary fuel level sensor and the signal circuit of the secondary fuel level sensor.
Connect a jumper wire between the ground circuit of the primary fuel level sensor and the ground circuit of the secondary fuel level sensor.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuits and the ground circuits of the fuel level sensors.
Turn the ignition ON, with the engine OFF.

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

Vary the resistance on the J 33431-C from 40-250 ohms.
Observe the fuel gage in the IPC.

Does the fuel gage move from empty to full?

Go to Step 4

Go to Step 3

Turn the ignition OFF.
Disconnect the fuel balance module.
Connect the J 33431-C between the fuel level sensor signal circuit of the PCM and the ground circuit of the fuel balance module.
Turn the ignition ON, with the engine OFF.

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

Vary the resistance on the J 33431-C from 40-250 ohms.
Observe the fuel gage in the IPC.

Does the fuel gage move from empty to full?

Go to Step 6

Go to Step 5

Inspect for the following items:

•	A poor connection at the harness connectors of the primary and the secondary fuel level sensors. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

•	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 20

Go to Step 8

Test the fuel level sensor signal circuit for an open, for a short to ground or for a high resistance between the fuel balance module and the PCM. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 10

Test the fuel level sensor signal circuits for an open, for a short to ground or for a high resistance between the primary and the secondary fuel level sensors and the fuel balance module. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 7

Test the ground circuits of the primary and the secondary fuel level sensors for an open or 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 20

Go to Step 14

Remove the primary and the secondary fuel level senders.
Inspect for the following items:

•	The primary or the secondary fuel level sensor is stuck, perhaps due to an interference with the fuel strainer.

•	The primary or the secondary fuel tank contains foreign material, for instance ice.

Did you find and correct the condition?

Go to Step 20

Go to Step 9

With the J 39200 DMM, measure the resistance of the primary and the secondary fuel level sensors while moving the float arm.
Observe both the analog and digital displays on the DMM.

Does the resistance for both fuel level sensors change smoothly across the specified range?

40-250 ohms

Go to Diagnostic Aids

Go to Step 16

Test the low reference circuit of the fuel balance module for an open or 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 20

Go to Step 11

Turn the ignition OFF.
Disconnect the PCM connector C2.
Connect the J 33431-C between the fuel level signal circuit and a good ground.
Turn ON the ignition, with the engine OFF.

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

Vary the resistance on the J 33431-C from 0-90 ohms.
Observe the fuel gage in the IPC.

Does the fuel gage move from empty to full?

Go to Step 15

Go to Step 12

Test the fuel level circuit for an open, for a short to ground, or 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 20

Go to Step 13

Inspect for poor connections at the harness connector of the IPC. 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 20

Go to Step 17

Inspect for poor connections at the harness connector of the fuel balance module. 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 20

Go to Step 18

Inspect for poor connections at the harness 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 20

Go to Step 19

Replace the fuel level sensor that did not have the correct resistance values. Refer to Fuel Level Sensor Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

Go to Step 20

Replace the IPC. Refer to Instrument Cluster Replacement

Did you complete the replacement?

Go to Step 20

Replace the fuel balance module. Refer to Fuel Sender and Balance Pump Control Module Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

Go to Step 20

Important:: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

Go to Step 20

Use the scan tool in order to clear the PCM DTCs.
Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2