Diagnostic Procedure

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.

CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten two ground screws on the body. Refer to Ground Inspection .
  
  Fig 1: DTC P1274, P1284 Loosening & Retightening Two Ground Screws On Body
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG
1. OK: GO TO 2.
2. NG: Repair or replace ground connections.
RETIGHTEN AIR FUEL RATIO (A/F) SENSOR 1
Loosen and retighten the air fuel ratio (A/F) sensor 1.

Fig 2: DTC P1274, P1284 Loosening & Retighten Air Fuel Ratio Sensor 1
Courtesy of NISSAN MOTOR CO., U.S.A.
1. Tightening torque: 50 N.m (5.1 kg-m, 37 ft-lb)
1. GO TO 3.
CLEAR THE SELF-LEARNING DATA.
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-II.
3. Clear the self-learning control coefficient by touching "CLEAR".
4. Run engine for at least 10 minutes at idle speed.
  Is the 1st trip DTC P0172 or P0175 detected? Is it difficult to start engine?
  
  Fig 3: Selecting "SELF-LEARNING CONT" In "WORK SUPPORT"
  Courtesy of NISSAN MOTOR CO., U.S.A.
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF.
3. Disconnect mass air flow sensor harness connector.
4. Restart engine and let it idle for at least 5 seconds.
5. Stop engine and reconnect mass air flow sensor harness connector.
6. Make sure DTC P0102 is displayed.
7. Erase the DTC memory. Refer to HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION .
8. Make sure DTC P0000 is displayed.
9. Run engine for at least 10 minutes at idle speed.
  Is the 1st trip DTC P0172 or P0175 detected? Is it difficult to start engine?
  
  Fig 4: DTC P1274, P1284 Disconnecting Mass Air Flow Sensor Harness Connector
  Courtesy of NISSAN MOTOR CO., U.S.A.
Yes or No
1. Yes: Perform trouble diagnosis for DTC P0172 or P0175. Refer to DTC P0172. P0175 FUEL INJECTION SYSTEM FUNCTION .
2. No: GO TO 4.
CHECK HARNESS CONNECTOR
1. Turn ignition switch OFF.
2. Disconnect A/F sensor 1 harness connector.
  
  Fig 5: DTC P1274, P1284 Disconnecting A/F Sensor 1 Harness Connector
  Courtesy of NISSAN MOTOR CO., U.S.A.
3. Check harness connector for water.
  1. Water should not exit.
OK or NG
1. OK: GO TO 5.
2. NG: Repair or replace harness connector.
CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT
1. Turn ignition switch ON.
2. Check voltage between A/F sensor 1 terminal 3 and ground with CONSULT-II or tester.
  1. Voltage: Battery voltage
OK or NG
1. OK: GO TO 7.
2. NG: GO TO 6.
Fig 6: DTC P1274, P1284 Checking Voltage A/F Sensor 1 Terminal 3 & Ground
Courtesy of NISSAN MOTOR CO., U.S.A.
DETECT MALFUNCTIONING PART
Check the following.
- Harness connectors M72, F102
- Harness connectors E108, M15
- IPDM E/R harness connector E7
- 15A fuse
- Harness for open or short between A/F sensor 1 and fuse
  1. Repair or replace harness or connectors.
CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Check harness continuity between the following terminals. Refer to Wiring Diagram.
  
  Fig 7: DTC P1274, P1284 Checking Harness Continuity In ECM Terminals Chart
  Courtesy of NISSAN MOTOR CO., U.S.A.
  1. Continuity should exist.
4. Check harness continuity between the following terminals and ground. Refer to Wiring Diagram.
  
  Fig 8: DTC P1274, P1284 Checking Harness Continuity In ECM Terminal & Ground Chart
  Courtesy of NISSAN MOTOR CO., U.S.A.
  1. Continuity should not exist.
5. Also check harness for short to power.
OK or NG
1. OK: GO TO 8.
2. NG: Repair open circuit or short to ground or short to power in harness or connectors.
CHECK A/F SENSOR 1 HEATER
Refer to Component Inspection .

OK or NG
1. OK: GO TO 9.
2. NG: Replace A/F sensor 1.
CHECK INTERMITTENT INCIDENT
Perform TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

OK or NG
1. OK: Replace A/F sensor 1.
2. NG: Repair or replace.