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Home >> Cadillac >> 2004 >> CTS Base, 3.2 N >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel System Displays, Gauges And Console >> Diagnostic Information and Procedures >> Fuel Gage Inaccurate or Inoperative >> Test Description

Test Description

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

  1. 3:  This step tests for a high resistance in the primary fuel level sensor signal circuit and the low reference circuit of the fuel level sensors.
  2. 4:  This step tests for a high resistance in the secondary fuel level signal circuit and the low reference circuit of the fuel level sensors.
  3. 18:  DTCs will be set in the engine control module (ECM) when you perform this diagnostic table.
Fuel Gage Inaccurate or Inoperative

Step Action Value(s) Yes No
Schematic Reference: Instrument Cluster Schematics 
Connector End View Reference: Engine Control Module (ECM) Connector End Views or to Inline Harness Connector End Views
1 Did you perform the Instrument Cluster Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Instrument Cluster 
2
  1. Turn the ignition ON, with the engine OFF.
  2. Install a scan tool.
  3. With the scan tool, perform the Displays Test in the IPC Special Functions Output Controls list.
Does the gage move from 0 to its maximum value and back to 0 when you perform the Displays Test?		 - Go to Step 3  Go to Step 16 
3 
  1. Disconnect C420, the fuel level sensor.
  2. Connect the J 33431-C  signal generator and instrument panel tester between the signal circuit of the Fuel Level Sensor Signal Primary and the low reference circuit of the fuel level sensors on the male terminal side. See Special Tools and Equipment .
  3. Turn the ignition ON, with the engine OFF.
    4. 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. With the scan tool, observe the Fuel Level Sensor Right Volts parameter in ECM EVAP Data list.
  6. Refer to Fuel Level Specifications  in order to convert from resistance to Fuel Level Sensor Right Volts.
Does the Fuel Level Sensor Right Volts parameter change smoothly across the specified range?		 0.7-2.5 V Go to Step 4  Go to Step 10 
4 
  1. Connect the J 33431-C  signal generator and instrument panel tester between the signal circuit of the Fuel Level Sensor Signal Secondary and the low reference circuit of the fuel level sensors on the male terminal side. See Special Tools and Equipment .
  2. Turn the ignition ON, with the engine OFF.
    3. 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. With the scan tool, observe the Fuel Level Sensor Left Volts parameter in ECM EVAP Data list.
  5. Refer to Fuel Level Specifications  in order to convert from resistance to Fuel Level Sensor Left Volts.
Does the Fuel Level Sensor Left Volts parameter change smoothly across the specified range?		 0.7-2.5 V Go to Step 5  Go to Step 11 
5 Inspect for the following items:
  • A poor connection at the harness connector of the suspect fuel level sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  • A high resistance in the Fuel Level Sensor Signal Primary signal circuit or the low reference circuit between the fuel level sensors and C420.
  • A high resistance in the Fuel Level Sensor Signal Secondary signal circuit or the low reference circuit between the fuel level sensors and C420.
  • A misaligned fuel level sender.
  • A deformed fuel tank.

Did you find and correct the condition?		 - Go to Step 18  Go to Step 6 
6
  1. Remove the primary fuel level sender.
  2. Inspect for the following items:
    • A stuck fuel level sensor

      For example: the fuel strainer interfering with the sender float arm.

    • Foreign material in the fuel tank, i.e. ice
Did you find and correct the condition?		 - Go to Step 18  Go to Step 7 
7
  1. With the J 39200  DMM, measure the resistance of the primary 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 Step 8  Go to Step 14 
8
  1. Remove the secondary fuel level sender.
  2. Inspect for the following items:
    • A stuck fuel level sensor

      For example: the fuel strainer interfering with the sender float arm.

    • Foreign material in the fuel tank, i.e. ice
Did you find and correct the condition?		 - Go to Step 18  Go to Step 9 
9
  1. With the J 39200  DMM, measure the resistance of the secondary 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 15 
10 Test the Fuel Level Sensor Signal Primary signal circuit for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 12 
11 Test the Fuel Level Sensor Signal Secondary signal circuit for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 13 
12 Test the low reference circuit of the fuel level sensors for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 13 
13 Inspect for poor connections at the harness connector of the engine control module (ECM). 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 18  Go to Step 17 
14 Replace the primary fuel level sensor. Refer to Fuel Level Sensor Replacement - Primary in Engine Controls.
Did you complete the replacement?		 - Go to Step 18  -
15 Replace the secondary fuel level sensor. Refer to Fuel Tank Module Replacement - Secondary in Engine Controls.
Did you complete the replacement?		 - Go to Step 18  -
16 Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement .
Did you complete the replacement?		 - Go to Step 18  -
17
IMPORTANT: Program the replacement ECM.
Replace the ECM. Refer to Engine Control Module (ECM) Replacement in Engine Controls.Did you complete the replacement?		 - Go to Step 18  -
18 
  1. Use the scan tool in order to clear the ECM 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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