siegfriedkaiser1

Sienna Fog Sensor Error AC Issue

I'm having a weird issue with my 2021 Toyota Sienna Hybrid (27k kilometers). The error memory is storing a fog sensor error, so the air conditioning system won't switch on. This is causing the spray nozzles to freeze and the mirror heating to fail. Any ideas? I think it's probably a defective cable or plug connection but I'm not 100% sure.

A 2021 Toyota Sienna Hybrid is experiencing an issue where a fog sensor error prevents the air conditioning system from functioning, leading to frozen spray nozzles and non-working mirror heating. The suspected cause is a defective cable or plug connection. A suggestion was made to check the fuses and consider the Body Control Module (BCM) or humidity sensor circuit as potential culprits. Ultimately, a visit to a workshop confirmed the issue was due to a defective connector, which was repaired.

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4 comment(s)

I had a similar problem with my Sienna. The symptoms you describe sound very familiar. Did you check the relevant fuse?

Which fuse are you referring to? I checked the main fuses, but I didn't see anything obvious.

It's difficult to pinpoint the exact fuse without a diagnostic scan. However, given the interconnected nature of the systems affected (climate control, mirror heating, windshield defogging), it is highly probable the Body Control Module (BCM) is involved. It might be related to the humidity sensor circuit, a common cause for these electrical gremlins. To avoid making it worse, I would advise against extensive DIY troubleshooting and recommend a visit to a trusted workshop. A diagnostic scan should swiftly identify the malfunctioning component and confirm the appropriate remedy.

Thanks for the advice. I took it to the workshop, and it turned out to be a defective connector, just like I suspected. The repair cost 95€, which seems reasonable.

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TOYOTA

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SIENNA