O2 Sensor Recommendation please?

[jmonica]

Hey Everyone. Hope you are all doing well. I've been chasing CEL emission codes on my car for over a year now. I now get a P140, P141, p0420 and P0446. I am attempting to address the o2 sensor codes first. I will work on the P0446 later.
I'm done messing around with these cheap O2 sensors. I understand that they may not be the source of the current problem, but in an effort to rule it out and try to prevent having to replace it any time soon, because I bought yet another $25 sensor, I want to buy the correct, recommended sensor and I'm hoping you guys can tell me what the best option is?
1) Is the Bosch O2 sensor considered an acceptable replacement or should I buy a GM Sensor?

2) Also, even though I don't currently have a code on the upstream, it's also a cheap replacement so do you think I should also replace that, just for peace of mind? A month or two ago I had a heater circuit failure code (P0135) on the upstream sensor but that code went away.

Back story... I had major emissions problems a while back. The car was running extremely rich. Fuel mileage went way down and I had black soot coming from the tailpipe. After fixing those problems the power is back, the average fuel mileage is back to normal (16.8 MPG). No more black soot. I replaced the catalytic convertor and fixed an exhaust leak.

I replaced the upstream O2 sensor (What a B*&%$ that was until I learned how to best remove it.) I changed the spark plugs, vent and purge valves, fixed the wiring problem etc. The engine oil got dirty really fast, so I am change that.

So now as I said I have P0420, P0140, P0141 and a P0446. I really feel like I have a bad ground on the ECM because random problems crop up then go away like the P0135, but I am going to replace the O2 sensor(s) with the correct ones. Then I'll try to fix the P0446 and see where I am at.

I've been chasing different codes for a long time and and sometimes they go away before I get to them and that's making things very hard to troubleshoot so i want to just start ruling things out by buying the right parts.

Also, I had a a couple of Brake codes that I was chasing and that turned out to be a bad ground. I just don't know exactly where the ECM gets the ground for the O2 sensors, so I'll have to spend a lot of time trying to find all of the different grounds and trying to repair them. I don't believe the ECM is bad as a couple of people have tried to tell me.

I'm honestly not sure how to attack these problems at this point. There are a few guys on youtube who really know to diagnose these sorts of problems and if I had someone in my area who I knew wasn't going to just throw parts at it, I would bite the bullet and take it to them, but I don't know which shop I can trust has the knowledge to track down the source of the problem so I guess I'll just keep fumbling through it.

I've been driving around with an expired inspection sticker for about 6 months now and so its only a matter of time before I get busted. I'm just praying I can hold out long enough to get rid of the CEL and get it inspected before I get popped and they tow the car and leave me thumbing it home. That would be really bad because it's my only ride to work.

I had a pretty bad motorcycle crash a while back. That was my back up means of transportation. I'm in the process of piecing that back together, but it's not really a viable means of transportation when its snowing out. Its very frustrating not knowing who I can bring it to or being able to identify all of the problems myself.

 

[59840Surfer]

In all my 57 years as a mechanic and the last 30 of them and even up to today --- I never had a good Bosch Oxygen Sensor.
None!
Never!
Total waste of time and money.

I'm not going to read your epistle ('way too much prose, no meat") --- but I saw "Bosch" and "Oxygen Sensor" in the text as those words jumped out at me and I know they should never be in the same sentence, let alone paragraph or in your engine either.

 

[mrrsm]

Some Diagnostic Suggestions...

(1) Stick with using only GM - ACDelco OEM Parts and CONFIRM their SOURCE B4 You BUY:



(2) Obtain this VERY Inexpensive Infrared Temp Sensor Gun for $20.00 and with the Engine Warmed Up, Parking Brake SET and Wheels CHOCKED... Point the IR Temp Gun at the Front of the CAT Can and Take a Reading. Then do the same at the Rear Sections of the CAT Can. and Take a Reading. IF the Front Temp is MUCH HIGHER than the Rear... Then the CAT is POISONED from excessive Fuel Contamination and will need to be replaced. The REAR Temp on ALL CAT Cans should always be HIGHER than the readings from the Front areas once the CAT Can has reached its Operating Temperature:

https://www.amazon.com/dp/B0C9M5NB31/?tag=gmtnation-20

(3) Check your Exhaust Manifold Flange Lines for signs of any Broken Bolts or Cracks. Un-Metered Air entering the Exhaust Stream can cause the PCM to add Fuel to compensate for the Stoichiometric Air-Fuel Imbalance and can "POISON THE CAT". Also, Sticking or Clogged Fuel Injectors can dump Fuel that is NOT Atomized into the Cylinders and Out the Exhaust and will likewise, "POISON THE CAT". *IF* the CAT is also Clogged Up and Reducing Engine Power and needs to be replaced for that reason on a High Mileage Engine ...replacing the Exhaust Manifold, MLS Gasket and Bolts at the same time makes good sense. Your Engine Year may require a careful investigation to identify the correct Dorman Exhaust Manifold for Port Dimensions and to Identify the CORRECT KIT Part Number specific to the 2006 Trailblazer 4.2L Engine:



(4) THIS is just about The BEST Instructional Video around for Understanding O2 Trouble Code Diagnostics for both GM V8 and I6 Engines:

 

[Mooseman]

Definitely fix the O2 sensor before looking at the cat. The P0140 and P0141 are saying the post-cat sensor is dead. The P0420 is a direct result of that dead sensor. Once that is fixed, reset and monitor. Your cat is likely fine. If not, then look at the method @mrrsm described with the IR temp gun.

As for which brand sensor, as @mrrsm said, stick with ACDelco or original GM. Barring those, I've had good results with NTK. There's also Delphi however no longer a division of GM since 2017 and has changed hands a couple of times so unknown if their quality has held up or if it's even the same company anymore.

 

[Mike534x]

NGK/NTK ( same company) seem to be providing sensors for ACDelco now, the upstream one I purchased for the Trailblazer was an OEM Delco off RA (arrived into the ACD branded box) with an NGK stamp on it. I wouldn't hesitate to use Denso either, my Envoy is currently running both for the up/downstream and they've been solid for the last 4 or years they've been installed.

 

[jmonica]

Some Diagnostic Suggestions...

(1) Stick with using only GM - ACDelco OEM Parts and CONFIRM their SOURCE B4 You BUY:

View attachment 111661

(2) Obtain this VERY Inexpensive Infrared Temp Sensor Gun for $20.00 and with the Engine Warmed Up, Parking Brake SET and Wheels CHOCKED... Point the IR Temp Gun at the Front of the CAT Can and Take a Reading. Then do the same at the Rear Sections of the CAT Can. and Take a Reading. IF the Front Temp is MUCH HIGHER than the Rear... Then the CAT is POISONED from excessive Fuel Contamination and will need to be replaced. The REAR Temp on ALL CAT Cans should always be HIGHER than the readings from the Front areas once the CAT Can has reached its Operating Temperature:

https://www.amazon.com/dp/B0C9M5NB31/?tag=gmtnation-20

View attachment 111662

(3) Check your Exhaust Manifold Flange Lines for signs of any Broken Bolts or Cracks. Un-Metered Air entering the Exhaust Stream can cause the PCM to add Fuel to compensate for the Stoichiometric Air-Fuel Imbalance and can "POISON THE CAT". Also, Sticking or Clogged Fuel Injectors can dump Fuel that is NOT Atomized into the Cylinders and Out the Exhaust and will likewise, "POISON THE CAT". *IF* the CAT is also Clogged Up and Reducing Engine Power and needs to be replaced for that reason on a High Mileage Engine ...replacing the Exhaust Manifold, MLS Gasket and Bolts at the same time makes good sense. Your Engine Year may require a careful investigation to identify the correct Dorman Exhaust Manifold for Port Dimensions and to Identify the CORRECT KIT Part Number specific to the 2006 Trailblazer 4.2L Engine:

View attachment 111663

(4) THIS is just about The BEST Instructional Video around for Understanding O2 Trouble Code Diagnostics for both GM V8 and I6 Engines:

Hi! As always, great information THANK YOU. I ordered the GM Upstream sensor. Due to lack of time, last week I ordered the Bosch upstream sensor. I will return that, but I am having trouble figuring out the correct downstream GM sensor. Checking all of the usual sources, I am getting conflicting information. One site says the (213-3908) doesn't fit my vehicle. One says it does and one says "may not fit". sigh..
I did find a consensus on the NKT 21023 so I guess I'll go with that. Rock Auto says it's actual OE part, so hats comforting.

Thank You for all of your help. I will end this here due to the fact that it's been made clear my comments are overly loquacious. I will post my results of when I get this sorted out.
Have a great weekend!

 

[jmonica]

Definitely fix the O2 sensor before looking at the cat. The P0140 and P0141 are saying the post-cat sensor is dead. The P0420 is a direct result of that dead sensor. Once that is fixed, reset and monitor. Your cat is likely fine. If not, then look at the method @mrrsm described with the IR temp gun.

As for which brand sensor, as @mrrsm said, stick with ACDelco or original GM. Barring those, I've had good results with NTK. There's also Delphi however no longer a division of GM since 2017 and has changed hands a couple of times so unknown if their quality has held up or if it's even the same company anymore.

Thank You Moose! I ended up going with the NKT. As I mentioned above, Rock Auto labels it as an "Actual OE part". I will post my results.

I need to apologize for talking too much. It just helps me think things out I think and sure as heck can't talk to my Son who doesn't give a rats arse about cars or what's wrong with the. I don't mean to and I will be sure to keep my posts short moving forward. Thank You again for all of your help!

 

[jmonica]

In all my 57 years as a mechanic and the last 30 of them and even up to today --- I never had a good Bosch Oxygen Sensor.
None!
Never!
Total waste of time and money.

I'm not going to read your epistle ('way too much prose, no meat") --- but I saw "Bosch" and "Oxygen Sensor" in the text as those words jumped out at me and I know they should never be in the same sentence, let alone paragraph or in your engine either.

Thank You for your reply and help. I apologize of my post was too wordy.

 

[jmonica]

NGK/NTK ( same company) seem to be providing sensors for ACDelco now, the upstream one I purchased for the Trailblazer was an OEM Delco off RA (arrived into the ACD branded box) with an NGK stamp on it. I wouldn't hesitate to use Denso either, my Envoy is currently running both for the up/downstream and they've been solid for the last 4 or years they've been installed.

Thank You Mike. I went with your recommendation and purchased the NKT (21023) for the downstream sensor. I honestly wouldn't have considered that brand until I read your post and Rock Auto lists the part as an "Actual OE Part", so you appear to be spot on. Anyway Thank You Sir!