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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 177 (Instrument Panel System Displays, Gauges And Console) >> Diagnostic Information and Procedures >> Fuel Gage Inaccurate or Inoperative >> Test Description

Test Description

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

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

Step Action Values Yes No
Schematic Reference: Instrument Cluster Schematics 
Connector End View Reference: Instrument Panel, Gages and Console Connector End Views , Engine Controls Connector End Views for the 3.5L engine and Engine Controls Connector End Views for the 3.9L engine
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Disconnect C305.
  2. Connect the J 33431-C  Signal Generator and Instrument Panel Tester or SA9205Z  Decade Box between the signal circuit of the fuel level sensor and the sensor ground circuit of the fuel level sensor, male terminal side.
  3. Turn ON the ignition, with the engine OFF.
    4. IMPORTANT: Verify the J 33431-C  or SA9205Z  resistance settings with a DMM. See Special Tools .
  4. Vary the resistance on the J 33431-C  or SA9205Z  from 40-250 ohms. 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 ON the ignition, with the engine OFF.
    3. IMPORTANT: Verify the J 33431-C  or SA9205Z  resistance settings with a DMM. See Special Tools .
  3. Vary the resistance on the J 33431-C  or SA9205Z  from 40-250 ohms. Refer to Fuel Level Specifications  in order to convert from resistance to fuel level percentage.
    4. IMPORTANT: Turn OFF the ignition momentarily between the resistance settings in order to quickly update the scan tool display.
  4. With the scan tool, observe the Fuel Tank Level Remaining parameter in the engine control module (ECM)/powertrain control module (PCM) evaporative emission (EVAP) data list.
Does the scan tool display the correct fuel level %?		 - Go to Step 11  Go to Step 5 
4 Inspect for the following items:
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 .
Did you find and correct the condition?		 - Go to Step 13  Go to Step 6 
6 Test the sensor ground circuit of the fuel level sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 13  Go to Step 9 
7
  1. Remove the fuel level sensor.
  2. Inspect for the following items:
    • A stuck fuel level sensor (i.e. the fuel strainer interfering with the sensor float arm)
    • Foreign material in the gas 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 ECM/PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 13  Go to Step 12 
10 Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement for the 3.5L engine.
Did you complete the replacement?		 - Go to Step 13  -
11 Replace the instrument panel cluster (IPC). Refer to Control Module References for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the ECM/PCM. Refer to Control Module References for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 13  -
13 
  1. Use a scan tool in order to clear the ECM/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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