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96 V6

error code
P0143 02 Sensor Circuit Low Voltage (Bank I Sensor 3)

I was under the impression that I only had two 02 sensors; one in front of the cat and one behind the cat. So can anyone tell me where this sensor is? Is it one of the two that I said? SHould I just replace it or does this mean another problem?
 

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What kind of car?

Any O2 sensor that detects exhaust on cylinder #1 is identified as Bank 1 HO2S.

Sounds like you might have O2 sensors in the exhaust manifolds. If that is the case with single exhaust then Bank 1 - Sensor 3 is the one downstream (after) the catalytic converter.

Sounds like you have a scanner to read this code so you can try and clear it and see if it resets again or replace it. I've seen bad ones on new cars with low mileage.
 

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There,s probably 4 O2 sensors on your car, there is on my 96 4.3L Jimmy. 1 in each exhaust manifold, usually identified as bank 1 and bank 2 O2 sensor 1. Then there is one just before (bank 1 HO2 sensor 2), and one just after the cat (bank 1 HO2 Sensor 3). The only purpose of the last one is to monitor the efficiency of the cat. The ECM looks at the difference between the one infront of the cat, and the one behind the cat, and sets a code if the difference isn't greater than a set value.

It will eventually set the catalytic converter efficiency code. Does the car have about 100K on it? Thats about when my first cat went.
 

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MRBO68 - Just because you got that code doesn't neccesarily mean that you have a bad o2 sensor! That scan tool will point you in the direction of the problem, then you have to go find it. A low voltage code could mean a battery problem, or you could have a wiring harness fault. Be careful.
 
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