oxygen sensor question

[chrissbee77]

I have a 01 grand prix 3.8 n/s. i was wondering if they make anything that can eliminate the first oxygen sensor for my car. like a plug or bypass or something. i have changed it with a delco or delphi cant remeber which one and the system code keeps coming back on. i have talked to a tech at my gm dealer and he said to eliminate it. I have a new exhaust system,o2 sensor, egr valve, purge valve, full tune up with factory plugs and wires, new injectors and o rings, new mass,iacv,and temp sensor., just want the light to stay off and looking for this part.////

[tblake]

bypassing the pre cat O2 sensor would be a bad idea. The PCM uses it to command the proper air/fuel ratio.

What is the specific code that is popping up?

Check the vaccum hoses going to the MAP sensor and the O-ring on the PCV valve. Maybe replace the PCV valve if it never hase been replaced.

[GTP Dad]

This is a new one on me. The fuel air ratio for the engine is dependent on the front O2 sensor. Without the sensor you will burn fuel at a much higher rate. I know there is an O2 emmulator for the rear sensor but I have never heard of one for the front. You may want to check with the GM Tech to see how this is done.

If you find out how to eliminate the sensor please post it so the rest of us will know!

[Shorinjinn]

You should not remove or by pass th main O2 sensor is essential for your PCM to read the right signal, you can bypass the rear O2 sensor by adding a 02 emulator or reprogram your PCM and erasing the O2 sensor completely from you PCM write up, but your problem relays on a vacuum leak or you MAF acting up if it is showing lean.

[chrissbee77]

thank you for your ideas i will def, change the pcv valve and map sensor and also check for vaccum leak i will post my results. sorry my code is. p0420. and it went off today for about 10 min and then it kicked right back on and is still on...

[tblake]

If its a P0420, then you need a cat converter, have an exhaust leak, or your REAR O2 sensor is bad.

[chrissbee77]

the code keeps saying bank 1 or sensor 1. The cat covnerter was installed from the dealer about 4 months ago. Also someone said check the vacum line to the MAP sesor all i see is an electical plug on the sensor that sits over the PCV valve and that is new as well. ( my MAP sensor seperates into 2 pieces. so i think its broke 1st pieces comes apart with the electrical conecter still plugged in and the other piece stays in that little housing over the PCV valve).

thanks guys

[tblake]

I'm not sure on the MAP sensor. I think if it is not setting a DTC it should be fine. I'm pretty sure the P0420 code has nothing to do with a MAP sensor. Do you have any Mods? Or exhaust work other than the new cat converter? (u-bend delete?) Are you getting any other DTC's in conjunction with P0420?

I kept having a re-occuring P0420 after a high flow cat and zzp 2.5 inch downpipe was installed. I just removed the code from my PCM. In fact, I removed all the rear O2 sensor codes, so I could just unplug that back O2 sensor and everything would be fine.

[CrazyHorst]

If you are chasing O2 faults a good idea is to check out all the engine harness ground connections. The O2 sensor is a millivolt signal that can get corrupted more easily than other "full 12v" signals.

[wafrederick]

Do you over fill the gas tank when refilling?If you do this,stop and it will set it off.Do not ever top off a gas tank in an OBD II vehicle,evap system needs room.This happened to my grandma Rose's 2001 Saturn,set off an oxygen sensor code replacing the oxygen sensor 3 times and it was her topping off the gas tank.Never came back on after she stopped topping off the gas tank.

[BNaylor]

Gentlemen, let us not get off on a tangent. If the OP has solely a P0420 DTC then that is the 02 sensor post CAT converter. A MAP sensor or a vacuum leak will not cause this specific DTC to set. An exhaust leak may. The post CAT 02 sensor monitors strictly CAT converter efficiency. The oxygen storage capacity of the CAT converter is less than desireable.

Getting a P0420 DTC with exhaust mods like bigger downpipe, PEM or headers is common and most often not curable short of getting a 02 simulator or the PCM reprogrammed to preclude the P0420 DTC from ever setting. This will NOT affect whether the vehicle will pass emissions testing. I have two GM cars that passed with flying colors. One has the 02 simulator ('02 Olds Alero) and the other (my '97 GTP) has the PCM reprogrammed.

On any front (pre) CAT converter 02 sensor mods....forget it!!! You will never pass emissions testing and the car will run like crap in the closed loop mode of operation since it keeps air/fuel mixture ratio at the ideal 14.7:1. The front 02 sensor is NOT used in the open loop mode of operation. For example WOT and very moderate acceleration.

[chrissbee77]

thanks for all the responses. I do not have any MODS of anykind. ITs stock all the way around. I have checked the wires and they all seem to be grounded. Also i do tend to top off my gas tank. (i know, i know) i didnt realize that this could be an issue, so i will stop doing it. As far as anyting else the car runs great i am just so tired of looking at the check engine light. Also no other codes are being thrown just the oxyen sensor code. so i will keep looking...

[doctorhrdware]

I would check the wiring back to the ecm and see if there is a problem with that. That could be your issue.

[tblake]

Originally Posted by chrissbee77

...Also i do tend to top off my gas tank. (i know, i know) i didnt realize that this could be an issue, so i will stop doing it....

Don't worry about it. To my knowledge, topping off your gas will not cause a P0420 to trip. Maybe other emissions DTC's but not a P0420, so I doubt that is your problem. I always top mine off to the next 1.00 and have never had an issue.

[BNaylor]

Just to clarify is the DTC still P0420?

If so then your issue is the CAT converter or an issue with the exhaust system since both were replaced otherwise you are just wasting your time. Just because the dealer replaced the converter doesn't mean it isn't bad. Many in the part system are defective since GM admitted it had installed defective ones on 2001-2002 models with the VIN "K" or VIN "1" engines.