Fuel Level Sensor Signal Inspection

WARNING: This page is about a different car, the 2008 Infiniti FX45 and 2008 Infiniti FX35. However, it is still accessible from the selected car via links, so may be relevant.

Symptom:

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

NOTE: The following symptoms are not malfunctions.

Fuel gauge

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

CHECK COMBINATION METER INPUT SIGNAL

Select "METER A/C AMP" on CONSULT-III.
Using "FUEL METER" on "DATA MONITOR", compare the value of "DATA MONITOR" with fuel gauge pointer of combination meter.

COMBINATION METER INPUT SIGNAL

Fuel gauge pointer	Reference value of data monitor [lit.]
Full	Approx. 86
Three quarters	Approx. 70
Half	Approx. 48
A quarter	Approx. 25
Empty	Approx. 9

OK or NG

OK: GO TO 2.

NG: Replace combination meter.

CHECK FUEL LEVEL SENSOR (SUB) CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect unified meter and A/C amp. connector and fuel level sensor unit (sub) connector.
3. Check continuity between unified meter and A/C amp. harness connector (A) M56 terminal 28 and fuel level sensor unit (sub) harness connector (B) B40 terminal 1.
  28 - 1 : Continuity should exist.
4. Check continuity between unified meter and A/C amp. harness connector (A) M56 terminal 28 and ground.
  28 - Ground : Continuity should not exist.
  
  Fig 1: Identifying Checking Fuel Level Sensor (SUB) Circuit
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG

OK: GO TO 3.

NG: Repair harness or connector.
CHECK FUEL LEVEL SENSOR (MAIN.SUB) CIRCUIT
1. Disconnect fuel level sensor unit and fuel pump (main) connector.
2. Check continuity between fuel level sensor unit (sub) harness connector (A) B40 terminal 2 and fuel level sensor unit and fuel pump (main) harness connector (B) B39 terminal 2.
  2 - 2 : Continuity should exist.
3. Check continuity between fuel level sensor unit (sub) harness connector (A) B40 terminal 2 and ground.
  2 - Ground : Continuity should not exist.
  
  Fig 2: Identifying Continuity Between Fuel Level Sensor Unit (Sub) Harness Connector (A) B40 Terminal 2 And Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG

OK: GO TO 4.

NG: Repair harness or connector.
CHECK FUEL LEVEL SENSOR (MAIN) CIRCUIT
1. Check continuity between fuel level sensor unit and fuel pump (main) harness connector (A) B39 terminal 5 and unified meter and A/C amp. harness connector (B) M56 terminal 36.
  5 - 36 : Continuity should exist.
2. Check continuity between fuel level sensor unit and fuel pump (main) harness connector (A) B39 terminal 5 and ground.
  5 - Ground : Continuity should not exist.
OK or NG

OK: GO TO 5.

NG: Repair harness or connector.
CHECK FUEL LEVEL SENSOR

Check components. Refer to "FUEL LEVEL SENSOR UNIT ".

OK or NG

OK: 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. Repair or replace malfunctioning part, if necessary.

NG: Replace fuel level sensor unit.