Parts available give me two choices. O2 sensor and Air Fuel Ratio sensor. Which is it? Location is Front manifold pre cat.
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2003 Toyota Highlander Question: OBD II shows front upstream O2 Sensor is bad.
Answer #1ziptie12 July 04, 2012, 13:05Master
was it 'Toyota' or aftermarket 'parts' that asked you that question?I'd bet it was advance or autozone. It's an a/f sensor pre-cat , O2s , after (or in middle) of cat (downstream). one is for engine management the other is for emissions monitoring.(short explanation). Safer and less costly to keep your Toyota , all Toyota!!
Replycheifpod1, July 04, 2012, 14:58Rookie
Okay so you are saying manifold location pre-cat its called an a/f sensor and post cat its called an o2 sensor right?
Replyziptie12, July 04, 2012, 16:30Master
Yes and I'm also stressing the importance of an OEM part. (I understand the $ difference for what should be the same part , but they're not). As I said in my first response they perform different functions.