My 855 has 144k on it with the last timing belt change at 138k. This morning the check engine light came on for the first time I'm aware of. What does this mean? The car starts, runs strong as ever with no other perceptible problems. I can't help but think disaster is lurking. I was already planning an oil change this weekend. Is there any routine maintenance I can do while I have her up on the rack to make this go away? Help! Thanks.

Stopped at Auto Zone on my way home last night. The computer threw a P0133 code...02 sensor circuit...Slow response...Bank1, Sensor 1. The AZ guy showed me what he believed to be the O2 sensor, about dead center below the fire wall in the main exhaust tube. Is this an easy fix? Looks like, if I put the car up on some ramps, it's pretty easy to get to. Is this the right one? Thanks for all of your help.

the P0133 code does not necessarily mean your O2 sensor is bad.

there are a number of things to consider when you see this code, esp whether it recurs or not.

A search of the forum would have revealed some of my thoughts on this code from a few weeks ago:
http://www.brickboard.com/AWD/volvo/1365302/V70/p0133_connecting_dots_reverse.html
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1998 V70 AWD Turbo 195k+

Check engine light indicates there was an engine fault detected, probably not a lurking disaster. There is a code stored in the engine computer pointing to the problem. It must be read with a scanner. Any mechanic can do this. Better yet pop into any Advance Auto store or similar chain parts store and they will gladly bring out their scanner and read the code for you and tell you what it means.

The problem could be simple as a loose gas cap or maybe a bad Oxygen sensor. There are dozens of possibilities, some minor, some not. Routine maintenance will not fix it unless it targets the problem.

Report back.
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David Hunter

It could mean many things; to find out you need the code it threw. '96 is the first year after the under-the-hood light/switch method to read the codes, so you will need a code reader. I bought a cheap Aquus that works great.

I think a place like Autozone will read the code for free. Once you have the code, you can search the internet for "Volvo DTC code" to find out what it means. People here can tell you how to troubleshoot a particular code once you have it.