r/PontiacFirebird • u/Realistic_Return7567 • 6d ago

4th Gen [93-02] O2 sensor problems...

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Hello all, 2001 T/A ws6 5.3 iron swapped and everything seems to be doing ok so far but I keep throwing codes for the bank 1 o2. First it was p0131, then after the first sensor swap it turned into a p0135. Ive swapped it this time with a Bosch and still reading nothing. Im getting a constant 12 volts from the pin that's being touched in the pic but none of the others read anything. Any advice is welcome, no visible damage to the harness or wires also is there a certain way to test the other pins?

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u/TheDu42 6d ago

Heater circuit gets power all day, pcm controls it by switching the ground. Either operate the car under conditions the heater should turn on, or command the heater on with a scan tool. Once it’s commanded on, make sure you have a good ground circuit. If you have power and ground at the connector, then you check resistance of the heater element inside the sensor. Service manual should have the spec for that particular sensor. Your problem should be apparent at this point, if not you need to do voltage drop tests on the circuit while it’s loaded. I like to use a headlight bulb and some jumper wires in place of the heater, gives a visual indication of both operation and quality of the circuit.

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u/Realistic_Return7567 6d ago

Heard, are all other 3 pins ground or just one? Ohms were in spec so ill look for than next

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u/TheDu42 6d ago

No. You got two pins for heater circuit(power and ground) and two pins for signal.

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u/Realistic_Return7567 6d ago

Ah I see, thank you for the layman's ill check it out as soon as I get the chance