1. Check ECM Power Supply

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 ECM harness connector.
Check voltage between ECM terminal 121 and ground with CONSULT-II or tester.
1. Voltage: Battery voltage

OK or NG

OK: GO TO 3 .
NG: GO TO 2.

Fig 1: Check Voltage

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