Mass Air Flow Sensor

With CONSULT-III 

1. Reconnect all harness connectors disconnected.
2. Start engine and warm it up to normal operating temperature.
3. Connect CONSULT-III and select "DATA MONITOR" mode.
4. Select "MAS A/F SE-B1" and check indication under the following conditions.
   MASS AIR FLOW SENSOR
   
   

   Condition	MAS A/F SE-B1 (V)
   Ignition switch ON (Engine stopped.)	Approx. 0.4
   Idle (Engine is warmed-up to normal operating temperature.)	1.0 - 1.2
   2, 500 rpm (Engine is warmed-up to normal operating temperature.)	1.6 - 2.0
   Idle to about 4, 000 rpm	1.0 - 1.2 to Approx. 2.4(1)
   (1) Check for linear voltage rise in response to engine being increased to about 4, 000 rpm.

5. If the voltage is out of specification, proceed the following.
   1. Check for the cause of uneven air flow through mass air flow sensor. Refer to following.
      • Crushed air ducts
      • Malfunctioning seal of air cleaner element
      • Uneven dirt of air cleaner element
      • Improper specification of intake air system parts
   2. If NG, repair or replace malfunctioning part and perform step  2 to  4 again. If OK, go to next step.
6. Turn ignition switch OFF.
7. Disconnect mass air flow sensor harness connector and reconnect it again.
8. Perform step  2 to  4 again.
9. If NG, clean or replace mass air flow sensor.

Without CONSULT-III 

1. Reconnect all harness connectors disconnected.
2. Start engine and warm it up to normal operating temperature.
3. Check voltage between ECM terminal 51 (Mass air flow sensor signal) and ground.
   ECM TERMINAL 51 (MASS AIR FLOW SENSOR SIGNAL) AND GROUND
   
   

   Condition	Voltage V
   Ignition switch ON (Engine stopped.)	Approx. 0.4
   Idle (Engine is warmed-up to normal operating temperature.)	1.0 - 1.2
   2, 500 rpm (Engine is warmed-up to normal operating temperature.)	1.6 - 2.0
   Idle to about 4, 000 rpm	1.0 - 1.2 to Approx. 2.4(1)
   (1) Check for linear voltage rise in response to engine being increased to about 4, 000 rpm.

   Fig 1: Checking Voltage Between ECM Terminal 51 And Ground

   Courtesy of NISSAN MOTOR CO., U.S.A.
4. If the voltage is out of specification, proceed the following.
   1. Check for the cause of uneven air flow through mass air flow sensor. Refer to following.
      • Crushed air ducts
      • Malfunctioning seal of air cleaner element
      • Uneven dirt of air cleaner element
      • Improper specification of intake air system parts
   2. If NG, repair or replace malfunctioning part and perform step  2 to  3 again. If OK, go to next step.
5. Turn ignition switch OFF.
6. Disconnect mass air flow sensor harness connector and reconnect it again.
7. Perform step  2 to  3 again.
8. If NG, clean or replace mass air flow sensor.