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Test Description

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 3:  This step tests for a high resistance in the signal circuit and the low reference circuit of the fuel level sensor.
  2. 13:  DTCs will be set in the PCM when you perform this diagnostic table.
Fuel Gage Inaccurate or Inoperative

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 C101.
  2. 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 female terminal side of the connector. See Special Tools and Equipment .
  3. Turn the ignition ON, with the engine OFF.
    IMPORTANT: Verify the J 33431-C  resistance settings with a DMM. See Special Tools and Equipment .
  4. Vary the resistance on the J 33431-C  from 40-250 Ω. See Special Tools and Equipment .
  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 a scan tool.
  2. Turn the ignition ON, with the engine OFF.
    IMPORTANT: Verify the J 33431-C  resistance settings with a DMM. See Special Tools and Equipment .
  3. Vary the resistance on the J 33431-C  from 40-250 Ω. See Special Tools and Equipment .
  4. Refer to Fuel Level Specifications  in order to convert from resistance to fuel level %.
    IMPORTANT: Turn the ignition OFF momentarily between the resistance settings in order to quickly update the scan tool display.
  5. With the scan tool, observe the Fuel Level Sensor parameter in the PCM EVAP Data list.
Does the Fuel Level Sensor parameter 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 sensor. Refer to TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.
  • A high resistance in the signal circuit of the fuel level sensor or the low reference circuit of the fuel level sensor between the fuel level sensor and C101.
  • 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 sensor for a high resistance. 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 sensor for a high resistance. 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:
    • 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 
8
  1. With the DMM, measure the resistance of the fuel level sensor 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 Ω 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 sensor. Refer to FUEL TANK .
Did you complete the replacement?		 - Go to Step 13  -
11
IMPORTANT: Program the replacement IPC.
Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement .Did you complete the replacement?		 - Go to Step 13  -
12
IMPORTANT: Program the replacement PCM.
Replace the PCM. Refer to POWERTRAIN CONTROL MODULE .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 
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