So within the last couple of days I was noticing that my TRAC OFF light was on then just today I got a P0133 code which reads O2 sensor circuit slow response Bank 1 Sensor 1. When this happened it made the engine shake a bit but went away fairly quickly. Which I think is expected if a O2 sensor is going bad. I want to start with replacing the O2 sensor that is causing CEL to light so what O2 sensor is sensor 1? In addition to all this is my car is a 2001 cavalier z24 2.4L mods are a CAI, ported TB, and a header, if any of this matters. Any help is great.

Bank 1, Sensor 1 is the front sensor, either in the exhaust manifold or right after it (haven't ever really checked out an ld9). In any case it's the sensor BEFORE the cat. The sensor after the cat is Bank 1, Sensor 2.



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So today I replaced the front O2 sensor with a AC Delco sensor closest to engine after header and erased the codes it threw. And it is now running like a champ. Ac Delco sensor was kind of pricey though, $75.00. But hey you get what you pay for right!

Definitely the right call. Glad it's all worked out! You should see better fuel mileage now too



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He seems to answer all our questions right


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