Parts for your 2003 Toyota Wish-Temperature sensors

2003 Toyota Wish temperature sensors — what they do and how to look after them

Temperature sensors are absolutely used on the 2003 Toyota Wish. Technical references including the Toyota Electrical Wiring Diagram (EWD) for ZNE10G/ANE10G (2003) and Toyota New Car Features for the 1ZZ-FE and 1AZ-FSE engines detail multiple temperature sensors: an Engine Coolant Temperature (ECT) sensor (THW) feeding the ECM, an Intake Air Temperature (IAT) sensor integrated with the MAF, an Automatic Transaxle Fluid Temperature sensor inside the transmission, and separate climate-control sensors such as the ambient and evaporator temperature sensors managed by the A/C amplifier.

On the Wish, these sensors help the engine and climate systems behave properly across Aussie and Kiwi conditions. The ECT sensor tells the ECU how hot the engine is so it can trim fuel, spark timing and idle speed, run the radiator fans, and protect the engine if it’s getting too warm. The IAT sensor helps dial in fuelling and timing as the air coming through the snorkel changes with season and speed. The transmission’s fluid temp sensor manages shift strategy and protects the box when fluid gets hot towing or in city traffic. For comfort, the A/C’s ambient and evaporator sensors help the system cool quickly without icing the evaporator or blasting the cabin unnecessarily.

There’s no fixed replacement interval for temperature sensors, but they should be checked during servicing. Common clues they’re grumpy include:

• Hard cold starts, rough idle or a rich fuel smell
• Erratic temperature gauge behaviour or radiator fans stuck on
• Poor fuel economy, lazy shifts, or A/C that cycles oddly
• OBD-II faults like P0115–P0119/P0128 (ECT), P0711 (ATF temp), or A/C fault codes via the climate ECU

Good practice on a 2003 Wish service is:

1. Inspect connectors and looms at the thermostat housing/water outlet (ECT), the MAF body (IAT), in front of the condenser (ambient), and at the evaporator probe for corrosion or brittle plastics.
2. Test the ECT and IAT with a multimeter, resistance should match the Toyota thermistor curve at known temperatures.
3. If replacing, use quality OEM-equivalent sensors. For ECT, fit a new sealing washer, torque to the workshop spec (around 20 N·m is typical, confirm in the manual), and bleed the cooling system properly.
4. Renew coolant to the correct Toyota Long Life/Super Long Life specification to protect the ECT and reduce scale.
5. After any sensor work, clear codes and verify live data and fan operation with a scan tool.

Location notes: the ECT is typically at the water outlet/thermostat housing on the 1ZZ-FE or near the cylinder head outlet on the 1AZ-FSE, the IAT sits inside the Denso MAF on the intake, the ambient sensor is behind the grille, the ATF temp sensor is internal to the transmission valve body.

Where is the engine coolant temperature (ECT) sensor on a 2003 Toyota Wish?

On 1ZZ-FE models it’s threaded into the water outlet/thermostat housing near the top radiator hose at the front of the engine. On 1AZ-FSE models it’s mounted by the cylinder head water outlet. It has a two‑pin connector and a small sealing washer.

What fault codes point to a dodgy temperature sensor on the Wish?

Engine ECT issues commonly log P0115–P0119 or P0128. Intake air temperature faults appear as P0110/P0113/P0114. Transmission fluid temperature concerns may flag P0711. Climate-control sensors can store A/C amplifier codes retrievable via scan tool.

Does the A/C system have its own temperature sensors?

Yes. The Wish uses an ambient temperature sensor ahead of the condenser and an evaporator temperature sensor in the HVAC box. These help prevent evaporator icing and keep cabin temperatures steady without overworking the compressor.