Parts for your 2019 Toyota C-hr-Temperature sensors

Temperature sensors on the 2019 Toyota C‑HR: what they do and how to look after them

Temperature sensors are definitely used on the 2019 Toyota C‑HR. Toyota’s Repair Manual and Electrical Wiring Diagram for the 2ZR‑FAE petrol model list multiple temperature inputs to the ECM/TCM and HVAC ECU, including the Engine Coolant Temperature (ECT) sensor, the Intake Air Temperature (IAT) element integrated in the mass air flow meter, an ambient air temperature sensor ahead of the radiator, an A/C evaporator temperature sensor, an in‑car (cabin) temperature sensor, and a CVT fluid temperature sensor within the transmission. These are also supported by standard diagnostic trouble codes (e.g., P0115–P0119 for ECT), confirming their presence and function.

On a 2019 C‑HR, temperature sensors help the car warm up cleanly, sip fuel instead of guzzling it, and keep the cabin comfy in Aussie and Kiwi conditions. The ECT sensor tells the engine computer how hot the coolant is so it can set cold‑start enrichment, ignition timing and when to switch the radiator fans. The IAT helps trim fuelling as air density changes. The ambient sensor feeds both the dash display and the climate control, while the evaporator and cabin sensors stop the A/C from icing up and keep the set temperature steady. The CVT fluid temp sensor protects the transmission by adjusting line pressure and shift logic when things get hot under the bonnet.

• Engine Coolant Temperature (ECT): threaded into the water outlet/thermostat housing, two‑pin connector to the ECM.
• Intake Air Temperature (IAT): built into the MAF sensor in the intake tube.
• Ambient Air Temperature: mounted near the grille/condensor area.
• CVT Fluid Temperature: internal to the transmission valve body.
• Evaporator and Cabin Temp Sensors: part of the HVAC system behind the dash.

As part of regular servicing (every 10,000 km or 12 months is a common schedule here), it’s smart to check scan‑tool data from these sensors. Look for believable numbers: coolant near ambient when cold, then up around the thermostat rating once warm, IAT a touch above ambient, ambient reading matching the weather, A/C evaporator hovering just above freezing when cooling.

• Inspect connectors and looms for corrosion or rub‑through, especially near the front bumper after coastal drives.
• If cleaning the MAF (and thus the IAT element), only use MAF‑safe cleaner and let it dry fully.
• Replace the ECT sensor only if it’s out of spec or flagged by DTCs, catch and refill with the correct Toyota Super Long Life Coolant and bleed air properly.
• The ambient sensor is inexpensive and easy to swap if readings are obviously wrong.
• CVT temp faults usually indicate internal issues, address with proper diagnosis and CVT service rather than parts‑swapping.

Common symptoms of a dodgy temperature sensor include hard cold starts, high idle, poor fuel economy, the radiator fan running all the time, A/C cutting in and out, a whacky outside temperature display, or the CVT going into a protective mode on hot days. A quick scan and a few basic checks will usually pinpoint the culprit, saving guesswork and keeping the C‑HR feeling fresh on long Kiwi and Aussie runs.

Where is the engine coolant temperature sensor on a 2019 Toyota C‑HR?

On the 2ZR‑FAE engine it’s fitted to the water outlet/thermostat housing at the front of the engine, near the upper radiator hose connection. It has a two‑pin plug and threads into the housing. Access is from above with the engine cover off, a cool engine and a drain pan are recommended if removal is needed.

Can a faulty temperature sensor cause rough running or bad fuel economy?

Yes. If the ECT reads too cold, the ECM over‑fuels and idles high, chewing through petrol. If the IAT reads hot or cold incorrectly, fuelling trims go off, causing hesitation or a rich/lean condition. Ambient or HVAC sensor faults affect climate performance. A quick look at live data against the day’s ambient temperature is the fastest way to confirm.

Do any resets or relearns need doing after replacing a temperature sensor?

Generally, no special calibration is needed. Clear any DTCs, start from cold, and let the engine warm to operating temperature, then take a short drive so the ECM relearns trims. If the MAF (with IAT) was cleaned or replaced, letting it idle for a few minutes and driving gently for a couple of trips helps fuel trims settle. HVAC relearns typically occur automatically at key‑on.