Parts for your 2001 Daihatsu Terios-Temperature sensors

2001 Daihatsu Terios temperature sensors — what they do and how to look after them

Temperature sensors are absolutely used on the 2001 Daihatsu Terios. Factory workshop literature for the J1-series Terios (1997–2005) details an Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) sensor in the engine management, with related diagnostic trouble codes such as P0115–P0119 (ECT circuit range/performance) and P0110–P0114 (IAT faults). OBD‑II/ISO 15031-5 and SAE J1979 standards also require coolant temperature (PID 05) and intake air temperature (PID 0F) data, which the Terios ECU provides, confirming these sensors are fitted.

• Engine Coolant Temperature (ECT) sensor
• Intake Air Temperature (IAT) sensor
• Ambient temperature sensor for A/C control (varies by trim)
• Automatic transmission fluid (ATF) temperature sensor on auto models

On a 2001 Terios, the ECT sensor is a workhorse. It tells the ECU how hot the engine is so fuelling and ignition timing can be spot-on from cold start to a long motorway run. It also helps the ECU switch the radiator fan and can trigger limp-home protection if things get too toasty under the bonnet. The IAT sensor keeps tabs on incoming air temperature so the ECU can fine-tune mixture for crisp throttle response and better economy. If fitted, the ambient sensor helps the A/C decide when to cut the compressor, and the ATF temp sensor on autos shapes shift timing and line pressure for smooth changes.

As part of regular servicing, it’s smart to give these little thermistors some love. Check the ECT/IAT connectors for corrosion, green crust, or loose pins, a quick clean with electrical contact cleaner can sort flaky readings. Inspect the wiring where it passes near the thermostat housing and intake — heat and vibration can fatigue the loom. Keep coolant fresh (typically every 2 years or around 40,000 km, per common workshop practice) and bleed air properly, air pockets can fool the ECT and make the fan or gauge behave oddly. If you’re chasing rough cold starts, rich running, black smoke, the radiator fan running constantly, or a dash gauge that doesn’t make sense — plus codes like P0115–P0119 or P0110–P0114 — the temperature sensors and their wiring are prime suspects.

Replacing the ECT or IAT is usually straightforward. Work on a stone-cold engine, depressurise the cooling system before removing an ECT, catch any spilt coolant, and fit a new sealing washer/O‑ring as required. Tighten the new sensor snugly to the workshop spec rather than “by feel”. Clear fault codes, warm the engine, and confirm stable readings with a scan tool. Using quality, known-brand sensors helps avoid do-overs.

Popular questions

Where is the coolant temperature sensor on a 2001 Terios?
On most J1-series Terios, the ECT sensor sits on or near the thermostat housing at the front or side of the cylinder head. It has a small two-pin plug. Follow the upper radiator hose back to the engine — you’ll typically find the sensor right there.

What are the symptoms of a failing temperature sensor?
Common signs include hard cold starts, stalling right after start, poor fuel economy, rich smell or black smoke, radiator fan running all the time, an inoperative or erratic temp gauge, and check-engine lights with codes like P0115–P0119 (ECT) or P0110–P0114 (IAT). Wiring faults can mimic a bad sensor, so test before replacing.

Do manual and auto Terios models use the same sensors?
Both use ECT and IAT sensors. Auto models also monitor transmission fluid temperature inside the gearbox for shift quality and protection. The engine-side sensors interchange between manual and auto, but the transmission temp sensor is specific to automatic variants.