Fuel Gage Inaccurate or Inoperative. Isuzu Isuzu T-Series (Truck Line C) 2002

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2002 🢒 Isuzu T-Series (Truck Line C) 🢒 Body and Accessories 🢒 Instrument Panel, Gages, and Console 🢒 Fuel Gage Inaccurate or Inoperative

Fuel Gage Inaccurate or Inoperative Single Tank

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 sender resistance (0-90 ohms) to verify the fuel level sender operation. When the fuel tank is empty, the sender resistance is 0 ohms. When the fuel tank is full, the sender resistance is 90 ohms.

Test Description

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

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

Step

Action

Value(s)

Yes

Schematic Reference: Instrument Cluster Schematics

Did you review the system operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Instrument Panel, Gages and Console

Disconnect the fuel sender.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit and the ground circuit of the fuel level sender.
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.

Does the fuel gage move from empty to full?

Go to Step 3

Go to Step 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 to Connector Repairs in Wiring Systems.

•	A misaligned fuel level sender.

•	A deformed fuel tank.

Did you find and correct the condition?

Go to Step 11

Go to Step 6

Test the signal circuit of the fuel level sender for an open, for a short to ground or for a high resistance between the fuel level sender and the IPC. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 5

Test the fuel sender ground circuit 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 11

Go to Step 8

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

•	The fuel level sender 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 11

Go to Step 7

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

Does the resistance change smoothly across the specified range?

0-90 ohms

Go to Diagnostic Aids

Go to Step 9

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 11

Go to Step 10

Replace the fuel level sender. Refer to Duramax® Medium Duty Diesel Engine Manual.

Did you complete the replacement?

Go to Step 11

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 11

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

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 sender resistance (0-90 ohms) to verify the fuel level sender operation. When the fuel tank is empty, the fuel level sender resistance is 0 ohms. When the fuel tank is full, the fuel level sender resistance is 90 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 sender.

This step tests for a malfunction in the fuel level sensor signal circuit or the IPC.

Step

Action

Value(s)

Yes

Schematic Reference: Instrument Cluster Schematics

Did you review the system operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Instrument Panel, Gages and Console

Disconnect the primary and the secondary fuel level senders.
Connect a jumper wire between the signal circuit of the primary fuel level sender and the signal circuit of the secondary fuel level sender.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuits of the fuel level senders and the ground circuit of the fuel level senders.
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.

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

Go to Step 4

Go to Step 3

Turn the ignition OFF.
Disconnect the fuel sender and the fuel sender and transfer pump control module.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the fuel level sensor signal circuit and the ground circuit of the fuel sender and transfer pump control 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 0-90 ohms.

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

Go to Step 6

Go to Step 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 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 16

Go to Step 9

Test the fuel level sender signal circuit for an open, for a short to ground or for a high resistance between the IPC and the fuel sender and transfer pump control module. 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 signal circuits of the primary and the secondary fuel level senders for an open, for a short to ground or for a high resistance between the fuel level senders and the fuel sender and transfer pump control module. 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 7

Test the ground circuit of the fuel level senders 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 16

Go to Step 11

Test the ground circuit of the fuel sender and transfer pump control 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 16

Go to Step 12

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

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

•	The primary or the secondary fuel tank contain 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 senders while moving the float arm.
Observe both the analog and digital displays on the DMM.

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

0-90 ohms

Go to Diagnostic Aids

Go to Step 13

Inspect for poor connections at the harness connector of the fuel sender and transfer pump control 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 16

Go to Step 15

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

Replace the primary or the secondary fuel level sender that did not have the correct resistance values. Refer to the Duramax® 7800 Medium Duty Diesel Engine Manual.

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

Replace the fuel sender and transfer pump control module. Refer to the Duramax® 7800 Medium Duty Diesel Engine Manual.

Did you complete the replacement?

Go to Step 16

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2