Greetings.

My CHECK ENGINE light came on last summer while sitting in traffic on a hot day. (Dealer had a 2week wait to get me in. 2 days later the light went off. It did this a couple of times last summer. I had the codes read (O2 sensor slow response/or something similar). We cleared the codes and it stayed off for abt a month. Springtime, sitting in traffic on a hot day, it came back on.

Is it safe to say my O2 sensor is baked? And if so, does the non-Volvo generic sensor I've read so much about work okay? I plan to change it myself.

Thanks in advance.

"That O2 sensor will save you gas anyway...."

Which is what a gas station mechanic told me when I went ahead and bought a new O2 sensor which we didn't need. I was trying to pass smog with an '88 244. Since then, I figure it's good practice to replace the O2 sensor regularly (every 80-100k or so).

For the hassle of all the splicing you can order the factory front sensor from FCPGroton.com for $115 (part #15097). If you want the rear sensor its $108. Here's a link..... http://fcpgroton.com/volvo850oxygensensors.htm . They handle all the factory parts, including the E-code headlight lens if you don't already have that ($85 each). I'd just spend a few extra bucks and get the factory sensor with the new harness and plug already on it.


Mike

I replcaed my front sensor with the 15715 Bosch. It was $50 at Autozone. The sensor itself looks identical to the one for Volvo (Bosch 15097) but with a different connector. I just matched them both up on the table and spliced the original connector onto the new sensor and it has been working fine for a few months now.

The 15715 has the same length harness as the original also. I believe you can use 15717 as well, but the harness is a little shorter.

Based on my experience with my 96' 850T, it probably is going bad. You can find part numbers by searching for them in the forum, but the Bosch universal O2 sensor I used was from Autozone and it was a 15729 and I paid $65 for it in Atlanta. I have seen other folks use a different part number, so I don't know what the difference is. Keep in mind that you will have to cut and splice the 4 wires under the car since these universal kits do not come with the factory connector, but this is a lot cheaper that the OEM.

I have a 1996 855R and I'm having the same problem with one of my O2 sensors. The codes got set the first time last year about thanksgiving, took it in, said it was a bad front O2 sensor, reset the codes (ofcourse the codes got set again before the service), scheduled a service to get it fixed (along with the cat which was just about to go out of warrenty), but when they took a look at the sensor in question they said it looked just fine. After some more digging they found that several (2) vacuum seals on the intake were broken, and apparently this can cause the O2 sensor(s) to set codes indicating their failure. So I got the vacuum seals replaced, and everything was good up untill a couple weeks ago when I noticed the turbo wasn't giving as much boost... As luck would have it I had already scheduled the 80K inspection, so I waited.

Today it turns out that when the guys at seattle volvo started it up, the check engine light came on, and it was the front O2 sensor again... I guess the point to all this rambling is make sure its really the O2 sensor and not a broken vacuum seal, because in my case the codes were getting set every couple weeks until I got the seals replaced and now it's been about 6 months since the check engine light came on. This time I'm sure it's the O2 sensor, because seattle volvo said all the vacuum seals and intake system checked out.

Anyway, I hope this was helpful.

From what you described, it may possibly be the O2 sensors. Remember that there are 2 of them...front & back O2 sensors. On my car when this symptom occurred, I was told that it was the front O2 sensor that needed replacement. And it was diagnosed correctly since I have not had the check engine turned on ever since the replacement.