1. Check ECT Sensor Power Supply Circuit

WARNING: This page is about a different car, the 2004 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition switch OFF.
Disconnect engine coolant temperature (ECT) sensor harness connector.
Turn ignition switch ON.

Fig 1: Locating ECT Sensor
Courtesy of NISSAN MOTOR CO., U.S.A.
Check voltage between ECT sensor terminal 1 and ground with CONSULT-II or tester.
1. Voltage: Approximately 5V

OK or NG

OK: GO TO 2.
NG: Repair open circuit or short to ground or short to power in harness or connectors.

Fig 2: Check ECT Sensor Power Supply Circuit

G00875914

Courtesy of NISSAN MOTOR CO., U.S.A.