1999 S70 T5 O2 Sensor Replacement 2.3 liter plug location

[Eddystone]

This is just a note in case anyone does a search on this topic.

I replaced my downstream O2 sensor today. There are a number of things about the T5 2.3L engine that differ from the other engines, or at least from the non-turbo 1998 2.4L in my other car.

The location of the electrical connection for O2 sensors is underneath the plastic tube that runs from the air cleaner box to the turbo. If you disconnect the electrical connections near the MAF sensor, you can release the top of the air cleaner box and lift the flexible hose up which will allow you to access the connection, although it is tight.

The downstream sensor plug is on the right as you face the firewall/windshield. On my connector, there was a red plastic locking piece that must be slid perpendicular to the connector before the old plug will release. Fishing the cable up from the O2 sensor, you'll find that the factory runs both upstream and downstream cables through a single plastic retaining clip that attaches to single hole.

When you insert the plug into the receptacle, it is keyed so you can't insert it the wrong way. Finish by sliding the red plastic retainer back into place.

I had an O2 senor error which I cleared with an OBDII device. I'll have to drive the car for a while and see if it returns over time. However, the car seemed to idle more smoothly and seemed more responsive when driving. Could be my imagination, but I think that the computer is now managing the fuel/air ratio better with the new O2 sensor.

My car turned 148,000 miles just the other day. If your car is of a similar mileage, performance may improve with a new O2 sensor. I've heard they should be replaced every 100,000 miles.

I used one of the right-angle O2 sensor tools available from Amazon and chased the threads with a Lisle thread chaser. The O2 sensor was a genuine Bosch that I got at a pretty good price. The original O2 sensor seemed like it was frozen but broke loose with a good yank on standard 3/8 breaker that is no longer than a standard ratchet.