Parts for your 2020 Toyota Vitz|yaris-Temperature sensors

2020 Toyota Vitz/Yaris temperature sensors — what they do and how to look after them

Temperature sensors are absolutely used on the 2020 Toyota Vitz/Yaris. Toyota’s own technical literature confirms multiple temperature inputs are integral to these models: the Engine Coolant Temperature (ECT) sensor for engine management and fan control, an Intake Air Temperature (IAT) sensor (commonly integrated in the mass air flow meter), an outside air temperature sensor for the A/C system and dash display, an evaporator temperature sensor to prevent icing, and an automatic transmission/CVT fluid temperature sensor where fitted. These are documented across Toyota Technical Information System (TIS) resources, including the New Car Features (NCF) for late Vitz/Yaris and XP210-series Yaris, plus the Repair Manual and Electrical Wiring Diagram sections that cover SFI/engine control, air conditioning, and transmission controls.

On a 2020 Vitz/Yaris, temperature sensors quietly keep things sweet under the bonnet and in the cabin. The ECT sensor tells the ECU how warm the engine is, so it can set fuelling and ignition timing, manage idle speed when cold, and trigger the radiator fans. The IAT sensor lets the ECU adjust for hot or cold intake air, keeping performance and economy consistent. In the cabin, the outside air and evaporator temperature sensors help the climate control hit the temp you’ve dialled in without fogging or freezing the evaporator. On CVT/auto models, the transmission fluid temperature sensor tweaks shift strategy and protects the transmission when it’s working hard on hot Aussie or Kiwi days.

There’s no fixed replacement interval for these sensors, they’re generally “replace on condition”. As part of routine servicing, a good workshop will scan live data to confirm the ECT and IAT readings are plausible (for example, cold-soak values matching ambient, smooth warm-up traces, no spikes). They’ll also check connectors for corrosion, ensure coolant is fresh and at the correct concentration, and verify the radiator fans cut in at the right temperature. If the A/C isn’t behaving, they’ll inspect the ambient and evaporator sensors and related wiring.

When a sensor fails, you might see a check engine light, poor cold starts, rough running, the cooling fans stuck on, weak A/C, or odd transmission behaviour. Replacement is usually straightforward: ensure the engine is cool, relieve pressure where applicable, swap the sensor with a quality part, renew sealing washers/O-rings, and top up/bleed coolant as needed. After replacement, clear fault codes and recheck live data. On CVT models, follow the service manual procedure for fluid level setting at the specified temperature and any required relearns. Using genuine or reputable aftermarket parts and keeping coolant and connectors in good nick will see these sensors last for many years.

• Common clues: hard cold starts, rich fuel smell, fans running constantly, A/C not cooling evenly, or transmission feels “off”.
• Service tip: compare scan-tool ECT/IAT to ambient at first start, big mismatches point to a sensor or wiring fault.

FAQs

Does a 2020 Toyota Vitz/Yaris have an engine coolant temperature sensor?
Yes. The ECT sensor is a core input to the engine ECU for warm-up fuelling, ignition timing, idle speed, and radiator fan control. It’s typically threaded into the engine’s coolant passage. If it fails or reads erratically, the ECU may default to rich fuelling, the fans can behave oddly, and you’ll often see DTCs such as P0115–P0119.

How often should temperature sensors be replaced?
They’re not a scheduled replacement item. Replace only when faulty or damaged. During regular services, a scan of live data and a quick visual of connectors and coolant condition is usually enough. Most last the life of the vehicle if the cooling system is maintained and wiring stays dry and secure.

Can you drive with a faulty temperature sensor?
It might run, but it’s not a great idea. A bad ECT or IAT can make the engine run rich, hurt fuel economy, and risk overheating if the fans don’t behave correctly. On CVT models, incorrect fluid temperature readings can affect driveability and longevity. Get it checked and sorted promptly.