Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System Description
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 operates only for approximately 15 minutes.
Power is at all times supplied
- through 20A fuse [No. 77, and 78, located in the IPDM E/R]
- to rear window defogger relay terminals 3 and 6.
- through 15A fuse [No. 28, located in the fuse block (J/B)]
- to A/C and AV switch terminal 1.
- through 50A fusible link [letter F, located in the fuse block (J/B)]
- to BCM terminal 7.
With the ignition switch turned to ON or START position, Power is supplied
- through 10A fuse [No. 12, located in the fuse block (J/B)]
- to rear window defogger relay terminal 1.
- through 10A fuse [No. 1, located in the fuse block (J/B)]
- to BCM terminal 35.
- through 10A fuse [No. 6, located in the fuse block (J/B)]
- to A/C and AV switch terminal 2.
Ground is supplied
- to BCM terminal 8
- through body grounds E13, E26 and E28.
- to A/C and AV switch terminal 5
- through body grounds M14 and M78.
- to internal CPU of IPDM E/R terminals 14 and 45
- through body grounds E13, E26 and E28.
When A/C and AV switch (rear window defogger switch) is turned to ON, Ground is supplied
- to BCM terminal 69
- through A/C and AV switch terminal 16
- through A/C and AV switch terminal 5
- through body grounds M14 and M78.
Then rear window defogger switch is illuminated.
Then BCM recognizes that rear window defogger switch is turned to ON.
Then it sends rear window defogger switch signals to IPDM E/R and display control unit (with navigation) or display unit (without navigation) via DATA LINE (CAN H, CAN L).
When display control unit (with navigation) or display unit (without navigation) receives rear window defogger switch signals, and display on the screen.
When IPDM E/R receives rear window defogger switch signals, Ground is supplied
- to rear window defogger relay terminal 2,
- through IPDM E/R terminal 54,
- through internal CPU of IPDM E/R and IPDM E/R terminal 45.
- through body grounds E13, E26 and E28,
and then rear window defogger relay is energized.
When rear window defogger relay is turned ON,
Signals are transmitted,
- through rear window defogger relay terminals 5
- to rear window defogger terminal 1,
- Rear window defogger terminal 2, is grounded through body grounds B7 and B20.
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 door mirror defogger)
Power is supplied
- through rear window defogger relay terminals 5 and 7,
- through fuse block (J/B) terminal 2C,
- through 10A fuse [No. 8, located in the fuse block (J/B)],
- through fuse block (J/B) terminal 5B.
- to door mirror defogger (Driver side and passenger side) terminal 1.
Door mirror defogger (Driver side and passenger side) terminal 5 is grounded through body grounds M14 and M78.
With power and ground supplied, rear window defogger filaments heat and defog the rear window and door mirror defogger filaments heat and defog the mirror.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.