System Description

WARNING: This page is about a different car, the 2005 Nissan Xterra. However, it is still accessible from the selected car via links, so may be relevant.

The rear window defogger system is controlled by BCM (body control module) and IPDM E/R (intelligent power distribution module engine room).

The rear window defogger only operates for approximately 15 minutes. Power is supplied at all times

through 15A fuses (No. 46 and 47, located in the IPDM E/R)
to rear window defogger relay (located in the IPDM E/R)
through 50A fusible link [letter g, located in the fuse block (J/B)]
to BCM terminal 70
through 15A fuse [No. 43 (with heated mirrors), located in the IPDM E/R]
to heated mirror relay (located in the IPDM E/R).
With the ignition switch turned to ON or START position, power is supplied
through ignition relay
to rear window defogger relay (located in the IPDM E/R)
through 10A fuse [No. 1, located in the fuse block (J/B)]
to BCM terminal 38.
With the ignition switch turned to ON position, power is supplied
through 10A fuse [No. 8, located in the fuse block (J/B)]
to front air control terminal 6.
Ground is supplied
to BCM terminal 67
to front air control terminal 20
through body grounds M57, M61 and M79
to IPDM E/R terminals 38 and 59
through body grounds E9, E15 and E24.
When front air control (rear window defogger switch) is turned to ON, ground is supplied
to BCM terminal 9
through front air control terminal 11
through front air control terminal 20
through body grounds M57, M61 and M79.
Then rear window defogger switch is illuminated.

Then BCM recognizes that rear window defogger switch is turned to ON.

Then BCM sends rear window defogger switch signals to IPDM E/R via CAN communication (CAN-H, CAN-L).

When IPDM E/R receives rear window defogger switch signals, ground is supplied
to rear window defogger relay (located in the IPDM E/R)
through IPDM E/R terminals 38 and 59
through body grounds E9, E15 and E24.
Then rear window defogger relay is energized, power is supplied
through IPDM E/R terminal 60
to rear window defogger terminal +.
Ground is supplied
to rear window defogger terminal -
through body ground D603.
With power and ground supplied, rear window defogger filaments heat and defog the rear window.

When rear window defogger relay is turned to ON (with heated mirrors), power is supplied
through heated mirror relay (located in the IPDM E/R)
through IPDM E/R terminal 23
to door mirror defogger (LH and RH) terminal 1.
Door mirror defogger (LH and RH) is grounded through body grounds M57, M61 and M79.

With power and ground supplied, rear window defogger filaments heat and defog the rear window and door mirror defogger filaments heat and defog the mirrors.