Yaris solar sensor fault

Sounds like a faulty solar sensor, also sometimes called a daylight sensor or HVAC sensor. These are used to adjust the climate control based on sunlight. Have you checked the sensor itself? It's usually located on the dashboard near the windshield. Give the cable and plug a wiggle and see if that changes anything.

Thanks for the tip. I'll check the sensor's location. When you say 'changes anything', what exactly should I be looking for? Should the error code disappear, or should the heating output improve immediately?

What I mean is that wiggling the connector might temporarily fix a bad connection, or make it worse, indicating a loose or corroded pin. If the connection is the issue, you might see the heating working better for a moment, or the error might clear after a reset. But honestly, if it's a bad connection, it's probably best to have it looked at by a workshop. A proper diagnostic check can pinpoint the problem.

I appreciate the advice. I took it to the workshop, and they confirmed a defective cable/plug connection to the solar sensor. Repair cost was 95€. Thanks again for pointing me in the right direction!