Parts for your 1999 Daihatsu Gran move-Temperature sensors

1999 Daihatsu Gran Move Temperature Sensors: What They Do and When to Replace

Based on recognised technical references — including the Daihatsu G3-series (Pyzar/Gran Move) workshop manual engine management section, the Daihatsu Electronic Parts Catalogue for G30x models, and common aftermarket catalogues (e.g., ADL Blue Print/Intermotor listings for 1996–2002 Gran Move) — the 1999 Daihatsu Gran Move is fitted with multiple temperature sensors. These include the engine coolant temperature (ECT) sensor used by the ECU, a dash gauge sender, an intake air temperature (IAT) sensor integrated with the EFI system, and a thermo-switch or sensor input for radiator fan control. Temperature sensors are therefore absolutely relevant to this vehicle.

On a 1999 Gran Move, temperature sensors are the quiet achievers that keep the engine running sweet as. The ECT sensor tells the ECU how hot the engine coolant is, so fuelling and ignition timing suit everything from a frosty start to a summer slog. The IAT sensor tracks incoming air temp to fine-tune mixture. There’s also temperature sensing for the radiator fan so it cuts in at the right moment. When these sensors age, owners might notice hard cold starts, rough idle, rich running, higher fuel use, lazy fan operation, or a temp gauge that doesn’t make sense.

Good servicing practice is to give the temperature-sensor circuit a quick check whenever coolant is changed or the throttle body/airbox is off. That means:

• Inspecting connectors for corrosion, broken locks, or oil/coolant wicking up the loom.
• Scanning live data to compare ECT and IAT against ambient when stone cold, they should read close to outside temperature.
• Verifying the radiator fan cuts in/out consistently after warm-up.

Replacement is straightforward if one proves faulty. Always start with a cool engine. For the ECT sensor, drain a little coolant to sit below the sensor level, unplug the connector, and remove the sensor. Fit a new sealing washer/O-ring as supplied, and tighten to manufacturer specification — not gorilla tight, as the alloy housing can crack. Refill with the correct coolant mix, run the engine with the heater on HOT, and bleed air until the upper hose is hot and the level stabilises. Clear any fault codes and confirm the new readings with a scan tool.

Because erratic temperature data can mimic a crook thermostat or a weak coolant mix, it’s smart to test before throwing parts. A decent multimeter and an infrared thermometer make quick work of diagnosis, and most owners appreciate the improved starting, economy, and fan behaviour once the system is reading true.

Popular questions about 1999 Daihatsu Gran Move temperature sensors

Where is the engine coolant temperature (ECT) sensor located?
On most 1999 Gran Move engines, the ECT sensor threads into the coolant passage near the thermostat housing or cylinder head outlet, close to the upper radiator hose. It has a two‑pin connector. There may also be a separate single‑pin sender for the dash gauge nearby.

Access is typically under the bonnet on the timing-belt end of the engine. A torch and a small mirror help to spot the connector clip before removal.

Can a faulty temperature sensor cause high fuel use or hard starting?
Yes. If the ECT reads colder than reality, the ECU enriches the mixture like it’s on choke, wasting fuel and sooting plugs. If it reads too hot, cold starts can be cranky and stumble-prone. IAT faults can also skew fuelling, especially in stop–start city driving.

A quick scan of live data when the engine is cold should show ECT and IAT close to ambient. If they’re wildly off, testing or replacement is on the cards.

Does the cooling system need bleeding after replacing the ECT sensor?
Usually, yes. Any time the cooling circuit is opened, air can get trapped. Refill with the correct coolant, run the engine with the heater on HOT, and massage the upper hose to purge bubbles. Top up once the thermostat opens and the fan has cycled.

Watch the temperature gauge and verify there are no leaks around the new sensor and its seal.