Fuel Gage Inaccurate or Inoperative. GMC Truck GMC C-Series Medium Duty Truck B7 2001

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C-Series Medium Duty Truck B7 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Fuel Gage Inaccurate or Inoperative

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.

•	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 and when the fuel tank is full the fuel level sender resistance is 90 ohms.

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

Does the fuel gage move from approximately empty to approximately 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 poor connection at the case ground 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 10

Go to Step 5

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 10

Go to Step 7

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 materials, for instance, ice

Did you find and correct the condition?

Go to Step 10

Go to Step 6

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

Does the resistance change smoothly across the specified range?

0-90 ohms

Go to Diagnostic Aids

Go to Step 8

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 10

Go to Step 9

Replace the fuel level sender. Refer to Fuel Sender Assembly Replacement in Engine Controls - 8.1L or to the Cat® Medium Duty Diesel Engine Manual - LG5.

Did you complete the replacement?

Go to Step 10

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2