Parts for your 1998 Mitsubishi Lancer-Temperature sensors

1998 Mitsubishi Lancer temperature sensors — what they do and how to look after them

According to the Mitsubishi Lancer CE workshop manual (1996–2003), Gregory’s Service & Repair Manual for Lancer/CC–CE, and the Mitsubishi ASA electronic parts catalogue, the 1998 Mitsubishi Lancer is fitted with multiple temperature sensors. These include an engine coolant temperature (ECT) sensor for the engine control unit (ECU), often a separate single‑wire sender for the dash gauge, an intake air temperature (IAT) sensor (commonly integrated with the airflow meter on many trims), and on automatic models, a transmission fluid temperature sensor. So yes — temperature sensors are absolutely relevant and used on this model.

The ECT sensor is the big player. It tells the ECU how hot the engine is so it can sort cold‑start enrichment, ignition timing, idle speed, radiator fan operation, and fuel economy. The dash sender simply drives the gauge so a driver can spot overheating under the bonnet. The IAT sensor lets the ECU adjust fuelling and timing based on air density, improving drivability from a frosty Dunedin morning to a hot Perth arvo. Automatic variants also watch transmission temperature to protect the gearbox under load.

There’s no set replacement interval for these solid‑state parts, but they do age. Common clues include:

• Hard cold starts, rough idle, or thirsty fuel use
• Radiator fans running all the time or not at all
• Check‑engine light with ECT/IAT codes (e.g., P0115–P0119)
• Gauge behaving oddly despite normal cooling system behaviour

Good servicing practice is simple: keep connectors clean and snug, inspect wiring looms for brittleness, and maintain fresh, correct‑spec coolant so sensor tips don’t corrode. A quick scan‑tool check when the car is stone‑cold should show ECT close to ambient, if it’s wildly off, it’s time to test or replace.

When replacing an ECT sensor, do it with the engine cold. Avoid thread tape unless the service data calls for it — many sensors earth through the threads and seal with a crush washer. A typical process is:

1. Relieve pressure, drain a little coolant, unplug the connector.
2. Remove the sensor with a deep socket, swap the sealing washer, install the new unit.
3. Tighten to the factory torque from the workshop manual, reconnect, refill with OEM‑spec coolant, and bleed air with the heater on.

If the IAT lives in the airflow meter, clean only with proper MAF cleaner and never touch the element. Transmission temperature sensors are usually internal, confirm faults with diagnostics before planning repairs. Done right, these little sensors keep a ’98 Lancer running sweet and saving fuel across Aussie and Kiwi roads.

Where is the coolant temperature sensor on a 1998 Lancer?
The ECT sensor is typically screwed into the thermostat housing or coolant outlet at the cylinder head, near the upper radiator hose. Many Lancers of this era have two senders close together: a two‑pin sensor for the ECU and a single‑pin sender for the dash gauge.

Can a bad temperature sensor cause poor fuel economy?
Yes. If the ECT reads colder than reality, the ECU enriches the mixture as if it’s on cold start, bumping up fuel use and washing cylinder walls. If it reads too hot, it can cause lean running, pinging, or fans cycling oddly. Restoring a correct reading usually brings fuel trims and economy back into line.

Is it safe to drive with a faulty coolant temperature sensor?
It might run, but it’s not wise. A failed sensor can disable proper fan control, skew fuelling, and mask genuine overheating. That risks head‑gasket damage. It’s best to diagnose and replace the sensor promptly and confirm cooling fan operation after the fix.