When I reset the Check Engine light and it came back on between 40 and 150 miles later, I knew it was time to change the oxygen sensor. No degrade in fuel economy.
So I got the Bosch sensor for my ’97 850 T-5 (T=turbo) from one of the MVS sponsors, Bosch part #15062. It was around $90. I didn’t want to fiddle with the Bosch universal sensor, although some here have used that with success and thus saved money.
P80 O2 Sensor DIY Procedure
It’s an easy job to change rear oxygen sensor, really. No exotic tools necessary. I did my front sensor years ago without the fancy socket, and it went ok. Be safe under the car.
I’ve had an annoying P0422 code for months (catalytic converter efficiency). I reset it and it comes back on between 40 and 150 miles later. No degrade in fuel economy.
A sticker on the box says “Oxy Sensor R 850T CSV70 NA98”. Take that to mean what you will. In other words, this Bosch part might fit many/most of the gen 1 FWD Volvos.
Why rear O2 sensor and not a new cat. convertor? Oh because a new cat and labor are about 6x as expensive, and with 110k miles on the rear sensor there are posts here pointing that direction. Also, the cat does not rattle when tapping it, further evidence it’s not the cat.
The sensor came with the wiring, wiring shielding, and the harness. Even the clips positioned at various points were in the right spots. Made it easy.
Jack up the Volvo safely. I just did the left side and left right side wheels on the ground.
Remove the belly pan. Four easy 12mm bolts. I jacked it up, sprayed those with liquid Wrench, waited 10 minutes, the easily took off the pan. Then I blasted the O2 sensor threads with Liquid Wrench and waited a few hours. It still took a ton of force, but nothing more than a 3/8ths inch ratchet.
Looking toward the front of the car. Notice the belly pan is a clip location for the wire (still attached).
Here’s a shot of my fancy new 7/8ths inch oxygen sensor socket. Less than $10. Didn’t want to just cut the wires, you never know if a) the O2 sensor is indeed failed and b) if it’s not, if you’ll need one again.
There’s just barely enough room to slide a 3/8ths inch socket wrench into the socket. Just push it on.
Looking down into the engine bay, driver’s side. These are the rear (L) and front (R) O2 sensor harnesses. The rear harness is open. This is the hardest part in my opinion. Hard to get to from underneath, hard to get to from up top. Slide a flat blade screwdriver under the red tab and twist to open it.
New (top), and old.
It’s an easy job, really. No exotic tools necessary. I did my front sensor years ago without the fancy socket, and it went ok. Be safe under the car.
Change Rear Oxygen (O2) Sensor, 850 T5 Tutorial
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