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02 simulator- P0420 Help

This is a discussion on 02 simulator- P0420 Help within the Firebird / WS6 forums, part of the Vehicle Specific category; I have a 01 trans am ws6. I have been getting P0420 code and I replaced the 02 sensor after ...

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    02 simulator- P0420 Help

    I have a 01 trans am ws6. I have been getting P0420 code and I replaced the 02 sensor after cat. Still getting code. I noticed the 02 voltage on bank1 sensor 2 drops from 0.9 to 0.065 volts and fluctuates back and forth. Bank 2 sensor 2 stays around 0.8 volts. I also installed a simulator today to see if it would help and the voltage is still fluctuating from 0.9 to 0.065 volts. I assume the voltage dropping so low is setting the code. What should I look at next? Thanks

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    Moderator 98TransAmWs-6's Avatar
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    I would just get them tuned out if it were me.

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    Only thing I can think of is a problem in the wiring somewhere. I think I'm going to have to get it tuned out. How much do shops usually charge to tune out the rear 02's

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    Moderator 98TransAmWs-6's Avatar
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    IDK I know mail orders are usually $120-150 so if it were me I'd ignore it until I got some mods done like exhaust and headers and just get it all tuned at once. Then also get egr and other emissions codes tuned out.

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    I will look into that. I ended up hooking the 02 sensor back up earlier. I went to start the car up and got a P0352- P0354- P0356- P0358. Ignition coil malfunction on all cylinders on bank 2 of the engine. It barely ran. I turned it off and let it sit for a while and now its running fine. I have no idea what would of caused that. All I did was unplug and plug the 02 sensor.

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    Moderator 98TransAmWs-6's Avatar
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    Well that means your coils weren't firing maybe they were dislodged, the connection that is. I would check the connections on them all. That or a coil is on its way out.

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    The good news is that the after-cat O2 sensors do not have a feedback loop that affects how your engine runs. The only thing they can do is trigger the SES. A steady ready from an O2 sender is usually a sign of a defective sender. As you saw on your scanner, the mV should rapidly cycle up and down, more so with the front O2 senders. I would swap the rear O2 senders from side-to-side and see if the problem stays on that bank or moves with the suspect sender.

    Sounds like you have something funky going on. Has there been any recent work under the hood - other than messing with the rear O2 sender?

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    I replaced the original 02 sensor after cat on bank 1 and the voltage was still dropping as low as 0.065 v. I then put a simulator in place of the 02 and it was acting the same way with the voltage dropping low once in a while. On bank 2 after cat which I get no code the 02 stays around 0.750-0.850 v and never drops low. From what I understand the voltage on the downstream 02 should stay high and not be dropping down to 0.100 v

    As far as the ignition coil not firing on bank 2. I got a code for cylinder 2-4-6-8 coils malfunctioning. The car felt like it was only running on 4 cylinders. This was after I took the simulator out and plugged the 02 sensor back in and started the car up it acted up. I then turned the car off let it sit for a while and checked all the wiring and grounds under the hood for anything obvious. I did not see anything and I had not done anything under the hood. I then started the car up after about 30 mins and everything was fine. If one coil was going out would that affect all of them on that side? I'm also going to be doing a tune up later this week plugs and wires.
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    Super Moderator pajeff02's Avatar
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    Loose ground wire or fried harness?

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    Quote Originally Posted by pajeff02 View Post
    Loose ground wire or fried harness?
    I'm going to have to look into it and see if I can find anything.

    I just now checked the downstream 02's again with the scanner. And now bank 2 is acting like bank 1 with the voltages dropping on the downstream 02s. Anyone know what a normal voltages for the downstream 02's should be reading?
    Last edited by matt3200492; 01-29-2017 at 09:09 AM.

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    Low voltage equals lean and high voltage equals rich. Post-cat, your readings should be towards the lean side I would think and not fluctuate a whole bunch. This is straight from the Autotap instructions:

    Under normal operating conditions, the downstream O2 sensor should have little switching activity. But if the rate at which the downstream O2 sensor is switching starts to increase, it tells the OBDII system converter efficiency is dropping and there's a potential emissions problem. If the problem may cause emissions to exceed 1.5 times the federal limit, the Malfunction Indicator Lamp (MIL) will come on and the PCM will log a diagnostic trouble code for "catalyst is below threshold efficiency" (P0420, P0421, P0422, P0430, P0431 or P0432). The bottom line here is you have a bad converter -- unless the problem is something else like a bad oxygen sensor or open fuel feedback control loop.

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