Diagnostic Procedure

CHECK ECT SENSOR POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect engine coolant temperature (ECT) sensor harness connector.
  
  Fig 1: Locating Engine Coolant Temperature Sensor Harness Connector
  Courtesy of NISSAN MOTOR CO., U.S.A.
3. Turn ignition switch ON.
4. Check voltage between ECT sensor harness connector terminal 1 and ground with CONSULT-II or tester.
  
  Fig 2: Checking Voltage Between ECT Sensor And Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
  
  OK or NG
1. OK: GO TO 3 .
2. NG: GO TO 2.
DETECT MALFUNCTIONING PART
Check harness for open or short between ECM and engine coolant temperature sensor.
1. Repair harness or connectors.
CHECK ECT SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Check harness continuity between ECT sensor terminal 2 and engine ground.
  Refer to Wiring Diagram.
  
  Continuity should exist.
3. Also check harness for short to power.
  OK or NG
1. OK: GO TO 5 .
2. NG: GO TO 4.
DETECT MALFUNCTIONING PART
Check the following.
- Joint connector-20
- Harness for open between ECM and engine coolant temperature sensor
- Harness for open between TCM (Transmission Control Module) and engine coolant temperature sensor
1. Repair open circuit or short to power in harness or connectors.
CHECK ENGINE COOLANT TEMPERATURE SENSOR
Check resistance between engine coolant temperature sensor terminals 1 and 2 as shown in Fig 3 .

Fig 3: Checking Engine Coolant Temperature Sensor
Courtesy of NISSAN MOTOR CO., U.S.A.
1. OK: GO TO 6.
2. NG: Replace engine coolant temperature sensor.
CHECK INTERMITTENT INCIDENT
Refer to TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .
1. INSPECTION END