5. Detect Malfunctioning Part

WARNING: This page is about a different car, the 2004 Infiniti Q45. However, it is still accessible from the selected car via links, so may be relevant.

Check the following.

Harness connectors B5, M5
Harness for open or short between rear window defogger and door mirror defogger relay and combination meter
1. Repair open circuit or short to ground or short to power in harness or connectors.