Parts for your 1999 Mitsubishi Pajero-Temperature sensors

1999 Mitsubishi Pajero temperature sensors – what they do and how to look after them

Temperature sensors are absolutely fitted to the 1999 Mitsubishi Pajero. Mitsubishi’s Factory Service Manual for 1997–2000 Pajero/Montero models (engine management and cooling sections), the Mitsubishi ASA parts catalogue, and mainstream workshop data (e.g., Haynes and Autodata) all show multiple temperature sensors on this vehicle. Depending on engine (3.0/3.5 V6 petrol or 2.8 TD 4M40), the Pajero uses an engine coolant temperature (ECT) sensor for the ECU, a separate sender for the dash gauge on many variants, an intake air temperature (IAT) sensor (integrated with the MAF on V6 petrol), an automatic transmission fluid (ATF) temp sensor on autos, and ambient temp sensors for HVAC.

On this model, the ECT sensor is the star of the show. It tells the ECU how warm the engine is so it can sort cold-start enrichment, ignition timing, idle speed, thermo-fan control, and overheat protection. On the 4M40 diesel, ECT input also guides glow plug after-heating and fast idle. The IAT trims fuelling as the air warms up or cools down, helping drivability and economy. In auto models, the ATF temp sensor helps the transmission computer pick the right shift strategy and lock-up timing.

These sensors aren’t “service items” in the same way as filters, but they should be checked whenever the cooling system is serviced. A quick scan-tool look at live data is gold: when stone-cold, ECT should read close to ambient, at operating temp it’ll generally sit around the thermostat spec (roughly high-80s to low-90s °C), with the fans cutting in a little higher. Visual checks matter too—brittle connectors, green crust on terminals, damaged loom tape near the thermostat housing, or oil-soaked plugs can all skew readings.

Replace the ECT or IAT if there’s erratic data, hard starts, poor fuel use, black smoke on a diesel, an overactive radiator fan, a misreading gauge, or fault codes like P0115–P0119. Use quality coolant-safe thread sealant only if the manual calls for it, fit a new sealing washer/O-ring, and tighten to the factory spec. After ECT replacement, top up with the correct coolant mix, bleed the system, and confirm stable temps on a road test. For V6 petrol models where IAT is built into the MAF, avoid harsh cleaners on the sensor element. On autos, the ATF temp sensor lives inside the transmission and isn’t routinely replaced—keep the fluid fresh and the cooler clean, and it’ll stay happy.

• Handy tip for off-roaders: after water crossings, check and re-seal sensor connectors, a dab of dielectric grease helps keep moisture out.

Popular questions

Where is the coolant temperature sensor on a 1999 Pajero?
On most 3.0/3.5 V6 petrol models it’s threaded into the thermostat housing/water outlet at the front of the intake. Many have a second, separate sender for the dash gauge nearby. On the 2.8TDi 4M40, look near the top radiator hose outlet on the cylinder head. Access is straightforward with basic hand tools once the engine is cool.

How do you test a Pajero ECT sensor?
Use a scan tool to compare the cold reading to outside temperature, then watch it climb smoothly as the engine warms. No scan tool? Measure resistance across the sensor pins and compare to a temperature–resistance chart: typical NTC sensors read a few kilo-ohms around 20 °C and a few hundred ohms near 90 °C. Any wild jumps, open circuits, or readings that don’t match temperature point to a faulty sensor or dodgy wiring.

Does the 1999 Pajero have more than one temperature sensor?
Yes. Expect an ECT for the ECU, often a separate sender for the instrument cluster, an IAT (integrated with the MAF on many petrols), an ATF temperature sensor on autos, and HVAC ambient sensors. Each serves a different system, so one bad sensor can cause issues even if the others seem fine.