iQ Rear Window Defroster Failure

I own a Toyota iQ and had a similar issue with my rear window defroster. Did you check the fuses? A blown fuse can stop the heating coil, even if the system detects an error. Also, have you tested the voltage at the rear window heating element connector?

I checked the fuses for the rear window heating, and they're fine. I haven't done a voltage test at the heating element connector yet. Can you explain how to do that and what voltage range is acceptable?

Since you checked the fuses and still have problems, and given the error code and windshield heating issue, the discharged battery idea might be right. I had the same symptoms and a workshop confirmed a defective battery caused electrical issues.

Thanks for confirming a similar experience. I'll get the battery checked at a service facility. It was indeed defective. After replacement and clearing the error memory, the defroster repair was done. Cost was 290€.