From Jaguars, to Caddies to Subbies, I have always used Bosch O2 sensors on my cars. I also belong to different forums for all my cars. You have some people on the Subbie list that say, because Subarus are finicky, only NGK plug wires will work without throwing a code but I have had a different experience. An experience where other wires work just fine.

I have to replace a lazy upstream O2 sensor. I am reading where people are saying that Volvo's are finicky and only NTK O2 sensor or Volvo supplied O2 sensors will work.

Hm???????

An O2 sensor isn't a rocket science development and needs to give off a very minimal voltage reading. As long as good materials have been used the O2 sensor should give off a good oscillation wave. In my experience Bosch hasn't been a company that is known for using poor materials in an O2 sensor.

What's up with the Bosch / NTK discussions?

When I bought my Jagaur parts I learned that you could buy the jag part in the green box, pay $200 for it or buy the same part, made by the same manufacturer without the green box and pay $100.

Kind of like the Volvo supplied transmission fluid sold by Volvo at some insane price or buy the same thing Mobil 3309 for a lot less money. Same thing just doesn't have the Volvo branded bottle.

Personally I only use NTKs. I found this out when we had a Subaru that laughed at Bosch parts, only NTKs would work on it.
More recently, we purchased an 01 S60 that immediately threw a CEL after buying. Looking back through the PO's work orders, I saw he had a new cat put on the car a year earlier for the same code ( and cost $900+! ouch)... Anyways, I didn't see anything about the O2 sensors being swapped out so it was my first plan of attack. One (downstream) NTK sensor and the code vanished and has stayed away for 3k+ miles so far.

You are correct, OE parts can be replaced by other manufacturers. But you have to be careful where these parts are made as not all are quality parts.

Some of the Volvos came with Denso O2 sensors, so even Volvo has multiple suppliers.

What you want are plug and play O2 sensors. Improper soldering of the sensor wires can effect the voltage which is quite low.

Not all O2 sensors have the same sensitivity, and it is the Volvo software in the computer that requires very good sensors.
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My back feels better when I sit in a Volvo seat