A Comprehensive Prius Water Valve Sensor Buyer's Guide

All Toyota Prii models have a part called the water valve sensor, which is a small electronic device placed inside the water valve. Its job is to keep tabs on the water valve’s position and communicate the information to the ECU.

This buyer’s guide will teach you everything you need to know about water valve sensors, ways to detect a failing sensor, and how to replace the water valve if needed. 

What's A Water Valve Sensor, And Why Is It Important?

Prius water valve

The water valve sensor continuously monitors the position of the water valve and relays the information to the ECM to help the water valve perform accordingly with the engine. The water valve is an incredibly important part in the Prius because it helps regulate the flow of coolant in and out of the coolant storage tank. Without the valve, the engine won’t get the right amount of coolant and could either overheat or take too long to heat up. Without the sensor, the water valve won’t function properly. You can read more about the water valve sensor here.

Is Your Water Valve Sensor Failing? Here's How You Can Tell

It’s not uncommon for a water valve sensor in a Toyota Prius to fail. Common symptoms include a rough idle, reduced engine power, a thumping or ticking sound coming from the engine, and more. Check out this comprehensive guide to diagnosing a failing water valve sensor to see if your water valve is failing.

How To Replace Your Prius Water Valve

Replace water valve

If you have a failing water valve sensor, the entire valve needs to be replaced. It’s a relatively straightforward project that should take a few hours. Once you have a genuine OEM water valve on hand (part no. 16670-21010 – you can buy one at a discount here), follow this step-by-step tutorial to replace your water valve.

Are OEM Water Valves Better Than Aftermarket?

You might be wondering whether you should get an OEM replacement water valve or an aftermarket water valve. OEM water valves are definitely the better choice because they’re manufactured to your Prius model’s specs, meaning the fitment is exact. They’re also generally made of better-grade materials and are backed by the Toyota parts warranty. OEM water valves are cheaper in the long run (especially if you buy from a reputable OEM Toyota parts seller like us), and they’re the better choice. Read more about this here.