Parts for your 2018 Mitsubishi Asx-Oxygen sensor

2018 Mitsubishi ASX oxygen sensor — what it does and how to look after it

Yes, the 2018 Mitsubishi ASX uses oxygen sensors. Technical references show the 2.0‑litre petrol ASX (GA2W series) is equipped with a front air–fuel ratio sensor (Bank 1 Sensor 1) in the exhaust manifold and a rear heated oxygen sensor (Bank 1 Sensor 2) after the catalytic converter. This layout is detailed in Mitsubishi Motors’ workshop manual for the RVR/ASX/Outlander Sport (Engine Control section) and reflected in the Mitsubishi parts catalogue listings (common part numbers include 1588A170 for the front A/F sensor and 1588A117 for the rear HO2S). The vehicle’s ADR 79/04 (Euro 5) emissions compliance and OBD requirements also necessitate these sensors.

On the 2018 ASX, the oxygen sensor setup quietly keeps things running sweet under the bonnet. The front sensor constantly reads oxygen content in the exhaust and lets the ECU fine‑tune the air–fuel mix. That helps the engine sit right on stoich for clean emissions, crisp throttle response and decent fuel economy on the school run or the motorway. The rear sensor keeps an eye on the catalytic converter’s performance, making sure it’s doing its job and flagging issues before they snowball.

They’re not a regular “every service” replacement item, but they do age. By around 100,000–160,000 kilometres, response can slow, mixtures can drift rich, and the cat can cop unnecessary heat. If the ASX starts using more petrol than usual, idles a bit rough, or pops a check‑engine light (common codes include P0131–P0139 or P0420), it’s time for a scan and a look at live data. A quick check for exhaust leaks upstream of the sensors and a visual on the wiring and connectors can save a lot of guesswork.

When replacing, stick with the correct ASX‑specific sensors rather than universal spliced types. Fit the front A/F sensor and rear HO2S in their original positions only. Most new sensors arrive with thread compound pre‑applied, if not, use a high‑temp oxygen‑sensor‑safe anti‑seize sparingly and keep it off the tip. Tighten to the manufacturer’s torque spec and route the leads away from heat. After install, clear codes and run an adaptation drive so trims settle properly.

• Good habits: fix any exhaust leaks early, keep the air filter fresh, use quality petrol, and don’t ignore a warning light.
• Service tip: at major services from 100,000 km, have a tech check sensor responsiveness and catalyst efficiency with a proper scan tool.

How many oxygen sensors does a 2018 Mitsubishi ASX have?

The 2.0‑litre petrol ASX typically has two: a front air–fuel ratio sensor (upstream) and a rear heated oxygen sensor (downstream). They work as a pair to manage fuelling and monitor the catalytic converter.

When should the oxygen sensors be replaced?

There’s no fixed interval, but from 100,000 km it’s smart to test them. Replace if there are fault codes, sluggish response on live data, obvious wiring damage, or after catalyst replacement. Many owners see best results swapping aged sensors around the 160,000 km mark.

Can a dodgy oxygen sensor cause high fuel use?

It can. A lazy or failed sensor can push the mixture rich, which chews through fuel and can overheat the cat. If consumption jumps and there’s a warning light, have the system scanned before it gets expensive.