Car: '94 855T 116,xxx miles

The "Check Engine" light's been on, and codes indicate O2 sensor. This is verified by dealer as well. Dealer (trustworthy based on prior experiences) suggested replacing both sensors b/c "when the front one goes, the rear usually goes soon after".

This car had the front sensor replaced early in its life--under New Car Warranty.

O2 Sensor replacement isn't too hard, so I'm willing to DIY. The question is whether I should do just the front, or both. Note that I'm coming up on mandated state emissions inspection, and a "Check Engine" is immediate failure, so this has to be fixed soon.

Thanks for your opinions...
-cj

I replaced only the front (heated) one indicated by the fault code and it worked fine. I used a "universal" type and saved some $$$. But do check for vac leaks.

Steve, I'm getting ready to replace the front sensor for my 96 850. Am a little ignorant on the subject. What do you mean by a universal type, and what was your source. Like you, I'm interested in saving $$$. Andy andyhoover@att.net

Whenever you get a O2 sensor code, the first things you should check are your vacuum hoses. Verify they are all in good health and all elbows are in good condition, too.

Volvospeed has some good pics on where to locate them all.

If you find any bad ones, replace them and reset your codes. If they come back, then explore new O2 sensor options.

-Jason D

'94 855 Turbo, Aretha, 96K

Whenever you get a O2 sensor code, the first things you should check are your vacuum hoses. Verify they are all in good health and all elbows are in good condition, too.


Right. Absolutely. That was my first diagnostic procedure. I found one, but code came back. The dealer used the smoke machine and found another and replaced it. Some other codes came back. They're indicative of O2 sensor failure, though only indicating the front one at the moment.

-cj

Ok, my next attempt would be the quick fix procedure found at http://au.geocities.com/ozbrick850/engine-o2-quickfix.html

I think the original was from this board, not sure who it was.

I did notice recently someone performed this and had good results:

http://www.brickboard.com/AWD/index.htm?id=464858

Worst case, you spend an hour doing this and it doesn't work. Then I'd replace. Best case, it works and you just saved yourself big $$

-Jason D