Parts for your 2018 Toyota Vitz|yaris-Temperature sensors

2018 Toyota Vitz/Yaris Temperature Sensors — What They Do and How to Look After Them

Temperature-sensors are absolutely used on the 2018 Toyota Vitz/Yaris. Toyota’s 2018 Vitz/Yaris Repair Manual and EWD (for XP130 series models such as KSP130/NSP130/NCP13#) detail several: the Engine Coolant Temperature (ECT) sensor in the SFI (engine control) section with DTCs like P0116–P0118, the Intake Air Temperature (IAT) thermistor integrated in the MAF sensor (P0111–P0113), an evaporator temperature sensor in the Air Conditioning manual (A/C amplifier controls, DTCs such as B1413), the outside air temperature sensor in the Meter/Gauge section, and, on CVT models, a CVT fluid temperature sensor referenced in the CVT diagnostics (P0710–P0713). These factory documents (Toyota Service Information/TIS) confirm the sensors are fitted and critical to engine, transmission and climate control operation.

On this Vitz/Yaris, temperature-sensors keep the whole show running sweet as. The ECT tells the ECU how warm the engine is so it can sort cold-start enrichment, idle speed and cooling fan control, and drive the dash gauge. The IAT helps fine-tune fuelling and ignition as intake temps change. The outside temp sensor feeds the display and helps HVAC logic, while the A/C evaporator sensor stops the core icing up. If it’s a CVT, the fluid temp sensor protects the transmission and manages shift/ratio behaviour.

There’s no routine replacement interval for these sensors, they’re serviced on condition. Good practice during regular servicing of your 2018 Toyota Vitz/Yaris temperature-sensors looks like this:

• Scan live data: compare ECT/IAT readings to ambient when cold, look for implausible values or fan behaviour.
• Inspect connectors and looms around the thermostat housing, MAF, front bumper (outside sensor) and CVT case for corrosion, broken clips or rub-through.
• If removing the ECT, capture a little coolant, swap the sensor and seal/O-ring, then refill with Toyota Super Long Life Coolant (pink) and bleed air.
• Clean the MAF/IAT with MAF-safe cleaner only, don’t touch the thermistor.
• For A/C faults (poor cooling, cycles off), check the evaporator sensor and drain for blockage before condemning parts.
• CVT over-temp or limp mode? Verify fluid level/condition and wiring, the sensor itself fails less often than the harness or fluid condition causes.

Typical symptoms of a crook temp sensor include hard cold starts, rich running, high fan duty, rough idle, ordinary fuel economy, A/C cutting in and out, a dodgy outside temp reading, or CVT warnings. Replacement is usually straightforward with basic tools and a scan tool to confirm the fix. Always use quality parts and correct torque to avoid cracking housings.

Popular questions

Where is the engine coolant temperature sensor on a 2018 Vitz/Yaris?
It’s mounted in the engine’s coolant outlet/thermostat housing area on the cylinder head side. Access varies by engine variant, but it’s typically reachable from the top with the intake ducting moved aside. Look for a two-pin connector on a small brass or plastic-bodied sensor threaded into the housing.

The best check is to follow the upper radiator hose back to the engine—near that outlet is where the ECT usually lives. A scan tool can confirm you’re on the right piece by watching ECT change as the engine warms.

Is the intake air temperature sensor separate on this model?
On most 2018 Vitz/Yaris variants, the IAT is integrated into the MAF sensor on the airbox or intake tube, so you replace the MAF assembly if the IAT fails. If diagnosing an IAT issue, inspect for unmetered air leaks first, then verify the MAF/IAT connector and pins before swapping parts.

Do temperature-sensors need periodic replacement?
No set interval. Replace only when testing shows a fault or when there’s physical damage. During services, verify readings, check connectors and, for ECT, ensure coolant is fresh and at the correct level—contaminated coolant and poor grounds can mimic sensor faults.