Fuel Gage Inaccurate or Inoperative. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Safari - 4WD 🢒 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.

Test Description

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

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

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

Step

Action

Value(s)

Yes

Schematic Reference: Instrument Cluster: Analog Schematics

Did you perform the Instrument Cluster Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Disconnect C310.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sensor and the low reference circuit of the fuel level sensor on the male terminal side of the connector.
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.

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

Go to Step 4

Go to Step 3

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 J 33431-C the 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 Level parameter in the PCM EVAP data list.

Does the Fuel Level parameter change from approximately 0 % to approximately 100 %?

Go to Step 11

Go to Step 5

Inspect for the following items:

•	A high resistance in the signal circuit or the low reference circuit of the fuel level sensor between C310 and the fuel level sensor.

•	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 misaligned fuel level sender

•	A deformed fuel tank

Did you find and correct the condition?

Go to Step 13

Go to Step 7

Test the signal circuit of the fuel level sensor 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 13

Go to Step 6

Test the low reference circuit of the fuel level sensor 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 13

Go to Step 9

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

•	A stuck fuel level sender (i.e. the fuel strainer interfering with the sender float arm)

•	Foreign material in the fuel tank (ice)

Did you find and correct the condition?

Go to Step 13

Go to Step 8

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 10

Inspect for poor connections at the harness connector of the VCM. 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 13

Go to Step 12

Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement in Engine Controls - 4.3L.

Did you complete the replacement?

Go to Step 13

Replace the IPC. Refer to Instrument Cluster Replacement .