Diagnostic Procedure

CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten two ground screws on the body. Refer to "GROUND INSPECTION ".
  
  Fig 1: Locating M28 & M54 Body Ground Screws
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG

OK: GO TO 2.

NG: Repair or replace ground connections.
CHECK ECT SENSOR POWER SUPPLY CIRCUIT
1. Disconnect engine coolant temperature (ECT) sensor harness connector.
2. Turn ignition switch ON.
  
  Fig 2: Disconnecting Engine Coolant Temperature (ECT) Sensor Harness Connector
  Courtesy of NISSAN MOTOR CO., U.S.A.
3. Check voltage between ECT sensor terminal 1 and ground with CONSULT-II or tester.
  Voltage: Approximately 5V
OK or NG

OK: GO TO 3.

NG: Repair open circuit or short to ground or short to power in harness or connectors.

Fig 3: Checking Voltage Between Terminal 1 And Ground
Courtesy of NISSAN MOTOR CO., U.S.A.
CHECK ECT SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Disconnect TCM harness connector (A/T models).
4. Check harness continuity between ECT sensor terminal 2 and ECM terminal 67, TCM terminal 42 (A/T models).
  Refer to WIRING DIAGRAM .
  
  Continuity should exist.
5. Also check harness for short to ground and short to power.
OK or NG

OK: GO TO 5.

NG: GO TO 4.
DETECT MALFUNCTIONING PART
Check the following.
- Harness for open or short between TCM and engine coolant temperature sensor (A/T models).
- Harness for open or short between ECM and engine coolant temperature sensor.
  : Repair open circuit or short to ground or short to power in harness or connectors.
CHECK ENGINE COOLANT TEMPERATURE SENSOR
Refer to "THERMOSTAT AND THERMOSTAT HOUSING ".

OK or NG

OK: GO TO 6.

NG: Replace engine coolant temperature sensor.
CHECK INTERMITTENT INCIDENT
Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".

: INSPECTION END