Fuel Level Sensor Signal Inspection

WARNING: This page is about a different car, the 2005 Infiniti G35. However, it is still accessible from the selected car via links, so may be relevant.

Symptom:

Fuel gauge indication is malfunction.
Low-fuel warning lamp indication is irregular.

NOTE: The following symptoms do not indicate a malfunction.

Fuel gauge

Depending on vehicle position or driving circumstance, the fuel in the tank flows and the pointer may fluctuate.
If the vehicle is fueled with the ignition switch ON, the pointer will move slowly.

Low-fuel warning lamp

Depending on vehicle position or driving circumstance, the fuel in the tank flows and the warning lamp ON timing may change.

CHECK HARNESS CONNECTOR
Check combination meter and fuel level sensor unit terminals (meter side, unit side, harness side) for looseness or bent terminals.

OK or NG
1. OK: GO TO 2.
2. NG: Repair terminal or connector.
CHECK COMBINATION METER CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect combination meter connector and fuel level sensor unit (sub) connector.
3. Check continuity between combination meter harness connector M19 terminal 7 (W/B) and fuel level sensor unit (sub) harness connector B28 terminal 1 (W/B).
  (W/B) - 1 (W/B): Continuity should exist.
4. Check continuity between combination meter harness connector M19 terminal 7 (W/B) and ground.
  (W/B) - Ground: Continuity should not exist.
OK or NG
1. OK: GO TO 3.
2. NG: Repair harness or connector.
  
  Fig 1: Checking Continuity Between Combination Meter Harness Connector M19 Terminal 7 (W/B) And Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
CHECK FUEL LEVEL SENSOR CIRCUIT
1. Disconnect fuel level sensor unit and fuel pump (main) connector.
2. Check continuity between fuel level sensor unit (sub) harness connector B28 terminal 2 (Y) and fuel level sensor unit and fuel pump (main) harness connector B27 terminal 2 (Y).
  2(Y) - 2 (Y): Continuity should exist.
3. Check continuity between fuel level sensor unit (sub) harness connector B28 terminal 2(Y) and ground.
  2(Y) - Ground: Continuity should not exist.
OK or NG
1. OK: GO TO 4.
2. NG: Repair harness or connector.
  
  Fig 2: Checking Continuity Between Fuel Level Sensor Unit Harness Connector B28 Terminal 2(Y) And Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
CHECK GROUND CIRCUIT
Check continuity between fuel level sensor unit and fuel pump (main) harness connector B27 terminal 5 (B/W) and ground.

5(B/W) - Ground: Continuity should exist.

OK or NG
1. OK: GO TO 5.
2. NG: Repair harness or connector.
  
  Fig 3: Checking Continuity Between Fuel Level Sensor Unit And Fuel Pump Harness Connector B27 Terminal 5 (B/W) And Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
CHECK FUEL LEVEL SENSOR
Check fuel level sensor units. Refer to "FUEL LEVEL SENSOR UNIT CHECK ".

OK or NG
1. OK: GO TO 6.
2. NG: Replace fuel level sensor unit and fuel pump (main) or fuel level sensor unit (sub).
CHECK INSTALLATION CONDITION
Check fuel level sensor unit installation, and check whether the float arm interferes or binds with any of the internal components in the fuel tank.

OK or NG
1. OK: Replace combination meter.
2. NG: Install fuel level sensor unit properly.