Parts for your 1998 Mitsubishi Lancer-Oxygen sensor

1998 Mitsubishi Lancer Oxygen Sensor — What It Does and When to Replace It

Yes, the 1998 Mitsubishi Lancer is fitted with an oxygen sensor (heated oxygen sensor/HO2S). This is documented in Mitsubishi Motors’ CE Lancer workshop/service information for the 1996–2003 models, which describes a heated oxygen sensor mounted in the exhaust, and is supported by listings in the Mitsubishi ASA electronic parts catalogue as well as Australian application guides from major suppliers like Bosch and NGK/NTK. Some variants run a single upstream sensor, markets with stricter on-board diagnostics may also have a second sensor after the catalytic converter.

On a 1998 Lancer, the oxygen sensor sits in the exhaust stream and constantly measures how much oxygen is left in the exhaust gases. The engine control unit (ECU) uses that signal to fine‑tune the air–fuel mix in closed‑loop operation. That helps the Lancer run smoothly, save fuel, and keep emissions in check. If the sensor goes lazy or fails, the ECU can’t correct the mixture properly, which often means higher fuel use, rough running, a whiff of fuel from the tailpipe, and the check‑engine light popping on.

For Aussie and Kiwi CE Lancers, most cars have a single upstream sensor screwed into the exhaust manifold or just before the catalytic converter. A few trims and markets add a downstream sensor to monitor the catalyst’s health. Either way, keeping the sensor healthy is an easy win for drivability and economy.

As part of routine servicing, it’s smart to:

• Inspect the sensor and wiring every 20,000–30,000 km for heat damage, frayed loom tape, or oil/road grime contamination.
• Scan for fault codes and check live data, a lazy sensor switches slowly or gets “stuck” rich/lean.
• Consider replacement around the 100,000–160,000 km mark, or sooner if symptoms show.

When replacing, only work on a cool exhaust, and use a proper oxygen‑sensor socket. Most quality replacement sensors come with thread compound on the bung, if not, apply a tiny amount of sensor‑safe anti‑seize to the threads only. Don’t touch the sensing tip, avoid silicone sealants near the intake or exhaust (they can poison the sensor), and check for exhaust leaks upstream of the sensor that could skew readings. After fitting, clear any codes, perform an idle relearn if needed, and take the Lancer for a steady drive so the ECU can settle back into closed‑loop.

A healthy oxygen sensor keeps the 1998 Lancer feeling perky, trims fuel nicely on highway runs, and helps the cat live a long, happy life under the car.

How many oxygen sensors does a 1998 Mitsubishi Lancer have?

Most Australian and New Zealand CE Lancers run a single upstream heated oxygen sensor before the catalytic converter. Some export or higher‑spec models also have a downstream sensor after the cat for catalyst monitoring. A quick look under the bonnet and along the front of the exhaust, or checking the VIN with a parts catalogue, will confirm which setup is fitted.

What are the signs the oxygen sensor needs replacing?

Common clues include higher-than-usual fuel use, sluggish response, rough idle, a sulphur or fuel smell from the exhaust, and an illuminated check‑engine light. A scan tool may show rich/lean codes or a slow‑switching HO2S signal. If the Lancer feels fine cold but plays up when warm, that also points to a tired sensor.

Can the oxygen sensor be cleaned, or should it be replaced?

Cleaning generally doesn’t restore a worn or contaminated sensor and can easily damage it. Given how critical the signal is to fuelling and emissions, replacement with a quality, correct-spec HO2S is the reliable fix. Once fitted, clear codes and verify closed‑loop operation on a test drive.