The Volvo 240/260 Pocket Data Book (1975-1993 green manual) lists the O2 sensor for all 1989-on LH systems (LH2.2/LH2.4/LH3.2) as Volvo p/n 3501753(3501753-2), Bosch p/n 0258003034 (aka the 13034 sensor). That was way back in 1993. The Bosch Auto catalog says 13308 is now their current fitment. Either one will work fine. They've got the full plug and play cable of the right length with the two OE 2 pin + 1 pin connectors and OE sensor design. Bosch is forever revising their part numbers for minor design or manufacturing changes. Parts houses and especially places like eBay may be selling older stock or using older Bosch p/n's that are functionally equivalent.

Note that Bosch makes two types of upstream (ahead of Cat) heated 3-wire O2 sensors at the moment. They're functionally equivalent electrically. Their more expensive Premium sensor has a bulb end with slits and is the OE design used by Volvo. The Premiumn sensors almost all come with vehicle connectors. Their cheaper Universal sensor uses a different sensor head with holes at the end of the nose. The Universal sensors mostly just come with pigtails that you splice to your old cable. Although they will both work in your car, my preference is to stick with the Volvo sensor style when available. It may be that design plugs less or burns off deposits slightly better or that the materials used in the sensor last longer or maybe it's just an older design or maybe it's a patent issue.

You can save a lot of money with universal fit sensors with pig tails that you splice to the original cable. Many brands are available of assorted quality, price and I assume longevity, but I always stick with Bosch. At the moment, the Bosch catalogue only lists 13757 with pigtails, but it has the Universal sensor head with the holes. The Premium slitted OE style used to be available with pigtails (I bought it once), but I'm not seeing it listed in parts houses at the moment. If you see one eBay for cheap I'd probably prefer it over the new Universal design. Another thing I've done is bought an O2 sensor for a different LH engine (B230 turbo vs NA) that was on sale for dirt cheap and cut the connector off. The only difference was the cable length.

Note that many do not recommend electrical paste or dielectric grease in the O2 sensor connectors, especially any connectors down by the cat. Some of that may be old wives tales about oxygen being able to breathe around the wires inside the harness, but that's BS. Way back 30+ years ago in a Volvo TSB I saw, they listed the connectors under the hood that should be moisture proofed with dielectric grease as part of scheduled maintenance and the O2 sensor was specifically excluded, but I've not seen an explanation for that. Since then I've avoided coating the connectors and never run into a problem.


Also for universal sensors with pigtails, because of the high heat and exposure to harsh conditions on the downpipe and down by the cat, it's best to avoid using aluminum crimp connectors, but rather use high heat nickel plated crimp connectors (sold in appliance repair stores for use on things like ovens). To weatherproof those connections you should use heat shrink, but note that there are different kinds and qualities of heat shrink out there. You want a decent quality waterproof heat shrink that's specifically designed to weather seal around the insulation. If you do use cheap heat shrink from an auto supplier, consider using two overlapped layers and making sure it's well away from the cat and hot exhaust pipes. Note that the Bosch 13537 Universal sensor is supposed come with special high heat electrical sleeve connectors and a connector block, although I've seen some suppliers list these without showing the connectors as included.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now