Parts for your 1997 Mitsubishi Pajero-Oxygen sensor

1997 Mitsubishi Pajero Oxygen Sensor: What’s Fitted and How to Look After It

Based on Mitsubishi’s 1997 Pajero/Montero factory service information, common parts catalogues from NTK/NGK and Bosch, and workshop data sources such as Autodata, oxygen sensors are fitted to petrol V6 models (3.0L 6G72 and 3.5L 6G74). Diesel variants of the same year—most commonly the 2.8L 4M40—do not use an oxygen (lambda) sensor.

Why some 1997 Pajeros don’t have one: the 2.8 turbo-diesel of that era meters fuel primarily via the pump and airflow, with EGR management but no closed-loop lambda control. Pre–common-rail diesels typically didn’t run an O2 sensor, so chasing an oxygen sensor on a 1997 4M40 Pajero isn’t relevant.

For petrol 1997 Pajero owners, the oxygen sensor is a small but crucial bit of kit. Sitting in the exhaust stream (usually one per bank on the V6, with some markets using a single upstream sensor and others adding a post-cat monitor), it constantly samples exhaust oxygen so the ECU can trim fuelling on the fly. The payoff is better fuel economy, smoother running, and cleaner emissions. When the sensor gets tired or contaminated, the ECU loses crisp feedback and the Pajero can feel a bit doughy off the mark, drink more fuel, or throw a check-engine light.

Signs it’s time to sort the sensor can include rough idle, flat spots, blackened tailpipe, or fuel use creeping up. Many tech references peg oxygen sensor life at around 160,000 km, but they can fail earlier if exposed to silicone sealants, leaded fuel, coolant or oil vapour. If the vehicle’s at that age or mileage, replacing the sensor as preventative maintenance isn’t a bad shout—especially if a scan shows lazy switching or rich/lean codes.

When replacing, stick with quality OEM-equivalent sensors from recognised brands. Fit the correct sensor for the engine code (6G72 vs 6G74) and market spec. Use the supplied anti-seize on threads only, avoid touching the tip, and torque to spec so it seals without stripping. After fitting, clear any fault codes and take it for a decent drive so the ECU can relearn trims. It also pays to check for exhaust leaks upstream, tidy any cracked wiring or tired connectors, and make sure the air filter and plugs are in good nick—closed-loop control works best when the basics are right.

• Typical service cue: scan for codes and sensor switching behaviour every major service (20,000–30,000 km).
• Good practice: fix vacuum or exhaust leaks before blaming the sensor.
• Note: some markets may have two upstream sensors, post-cat sensors (if fitted) monitor catalyst efficiency, not fuelling.

Popular questions

Does a 1997 Mitsubishi Pajero have an oxygen sensor?
Petrol V6 models do. Diesel 2.8 4M40 models don’t. Technical references (Mitsubishi service manuals and NTK/Bosch catalogues) list upstream lambda sensors for the 6G72/6G74 engines, while the 4M40 diesel of that vintage runs without one.

How often should the oxygen sensor be replaced?
There’s no hard-and-fast interval, but many workshops treat 160,000 km as a sensible trigger if performance or fuel economy is slipping. A scan showing slow switching or rich/lean codes is a good prompt to replace. Otherwise, inspect at major services and replace on condition.

Is it okay to drive a 1997 Pajero with a faulty O2 sensor?
It’ll usually still drive, but fuel economy will suffer and it may run rich, risking catalyst damage over time. Best bet is to diagnose promptly—rule out exhaust leaks, then replace the sensor if it’s proven sluggish or stuck.