I have a 1997 626 and the check engine light came on. Took it to my mechanic and he hooked it up to the computer. No code came up so he reset the light hoping this would fix it. It did for a couple of weeks.

It came on again and I took it to the mechanic again. He hooked it up to the computer and it said that the oxygen sensor was bad. Had it replaced. Two weeks later the light is back on.

any suggestions?

Hard to say without knowing what kind of engine and how many miles are on it. If you have over 60K miles on your car, you should replace them anyway.

I have a 97 626 also. There are 2 O2 sensors. one before the pre-cat and 1 after the pre-cat. Maybe your problem is with the one they didn't replace. BTW Autozone will read the code out for free.

I am having the same problem. I'm being told that it could be one of the 2 sensors or the cat converter. Mazda has a special warranty on the converters up to 127,000 km which unfortunately is no good for me. I haven't replaced any of these parts yet so I don't know if either will fix the problem. I do know it's alot of money to spend trying to find out.

thornhir, I purchased the universal one for my 1st o2 sensor(the one before the pre-cat) at oxygensensors.com. They were $50 back when I did it. Now they are $60. A lot cheaper than the dealer price. The drawback is that you have to splice it in to your existing wires. What I did was remove the old O2 sensor and just cut the connector off it (leaving plenty of wire) and spliced into it. There are 4 wires. comes with instructions if you are up for the challenge.. You will still have to reset your ECU by disconnecting your battery's negative terminal after you are done to reset your check engine light.

Jpit knows his stuff. My dad did the same thing on his '97 626, and fixed the thing with almost no hassle. Though, if i recall correctly, he cut his wires as close to the harness as possible (as opposed to the sensor) this left him with a small amout of wire to work with. After some cussing... he got it working.