Parts for your 1993 Mitsubishi Pajero-Oxygen sensor

1993 Mitsubishi Pajero oxygen sensor — used on petrol, not used on diesel

For a 1993 Mitsubishi Pajero, an oxygen sensor (lambda sensor) is fitted to petrol engines (e.g., 6G72 3.0 V6), but generally not used on the diesel variants (e.g., 4D56T 2.5 and early 4M40 2.8). This split is supported by factory service literature and parts catalogues that show an exhaust-mounted O2 sensor and closed‑loop control for EFI petrol models, while the mechanical/electronic diesel injection systems of the era run open‑loop without a lambda sensor.

• Mitsubishi Pajero/Montero Factory Service Manual (1991–1996), Engine Electrical/Fuel sections — petrol EFI shows O2 sensor feedback, diesel sections do not.
• Mitsubishi ASA Electronic Parts Catalogue (Gen II Pajero) — O2 sensor listed for 6G72 petrol, not listed for 4D56/4M40 diesels of the period.
• Bosch Automotive Handbook (Lambda Sensors, Diesel Emissions) — 1990s diesels typically operate excess-air without a three‑way catalyst, so no closed‑loop O2 control.
• ADR 37/01 (petrol) vs ADR 36 (diesel) emissions requirements of the early ’90s — petrol closed‑loop with cat, diesels not required to use three‑way catalysts.

If your 1993 Pajero is diesel: an oxygen sensor isn’t used because combustion is governed by injected fuel quantity with abundant excess air. Without a three‑way catalytic converter to manage, the ECU or mechanical pump doesn’t need lambda feedback. EGR and boost control are handled with other sensors and valves, so there’s simply no O2 sensor to service or replace.

For petrol 1993 Pajero owners, the oxygen sensor is a small but mighty bit of kit that keeps the 6G72 V6 running sweet as. Sitting in the exhaust stream, it measures how much oxygen remains after combustion, letting the ECU trim fuelling on the fly to hit the ideal air–fuel ratio. That means better fuel economy on long Kiwi or Aussie drives, smoother idle around town, and a catalytic converter that lives a long, happy life.

As part of regular servicing, it’s smart to give the O2 sensor a thought every 100,000–160,000 km, or sooner if you notice higher fuel use, a rough idle, flat spots, or the check engine light. A scan tool that shows fuel trims or O2 switching speed is gold for diagnosis. If the sensor’s lazy or the wiring is brittle from heat, replacement is the go.

When replacing, choose quality (Denso/NTK are common OEM suppliers), and match the connector style for your build year. Soak the threads beforehand, use an oxygen‑sensor socket, and don’t twist the harness. Most new sensors come pre‑coated, if not, apply a tiny dab of high‑temp anti‑seize to the threads only. Tighten to the workshop manual spec, clear any fault codes, and let the ECU relearn at idle. Also check for exhaust leaks ahead of the sensor — even a small leak can skew readings and undo your good work.

Keep the heat shields in place, route the lead away from the manifolds, and you’ll have a reliable sensor that keeps the Paj running spot on and saves a few bucks at the bowser.

FAQs

Does a 1993 Pajero diesel have an oxygen sensor?
Generally, no. The 4D56T and early 4M40 diesels of this era run excess air and don’t use a three‑way catalytic converter, so there’s no need for closed‑loop lambda control. Fuel delivery is managed by the injection pump and sensors other than an O2 sensor.

How many oxygen sensors does a 1993 Pajero V6 have, and where are they?
Most 1993 V6 models have a single upstream sensor fitted in the exhaust before the catalytic converter. Some later or market‑specific variants may add a downstream sensor, but for early‑’90s Pajero in AU/NZ, one pre‑cat sensor is the usual setup.

When should the oxygen sensor be replaced on a petrol 1993 Pajero?
There’s no hard expiry, but many owners replace them around 160,000 km or when symptoms appear: worse fuel economy, hunting idle, sluggish performance, or a stored fault code. If scan data shows slow switching or stuck readings, it’s time.