Outside Temperature Sensor Issue

That sounds like a faulty ambient temperature sensor or the wiring. The connector could be corroded, given the RX's age. Check the connector and wiring harness for damage, corrosion, or breaks. The sensor is usually near the front bumper, behind the grille. Check for power and ground at the connector. Do you have a multimeter and the wiring diagrams?

Thanks, that's helpful. I have a multimeter and some experience with wiring diagrams. Can you tell me which pins to test to confirm power and ground? If the reading is off, does that mean the sensor is bad, or could it still be a wiring problem?

Check the wiring diagram for your model year to be sure, since pin configurations can be different. You're generally looking for a 5V reference voltage and a good ground connection. A bad reading could be a wiring issue upstream, like a break or corroded connector. It might be best to take it to a workshop, since you might need a diagnostic scanner to figure out the sensor data.

Thanks for the advice. I had a mechanic check it. It was the outside temperature sensor, and they replaced it with some minor wiring repair at the connector. It cost 95€, and everything's working now.