02 sensor replacement???

[Lastplace]

Front on this model appears to be an A/F sensor, rear 02, both have been ordered. Both Densos, dealer wanted $250+ just for the 02. I verified part numbers on the Denso website before ordering.

Thanks to Timmy’s video looks like it will be a fairly easy repair.

All of my children went to FCHS.

 

[ragehell77]

hi my 98 3rd gen keeps throwing p0171 code we have replaced the
o2 sensor twice put new gaskets new hoses new everything but it just keeps revving when in park. my husband is about to give up and sell it but i love this truck sooo could this A/F sensor be the problem...?PLEASE CAN YOU HELP ME KEEP MY TRUCK contact me at [email protected]

 

[brisamh]

Today i had finished the rest of the job (to be fair, the hard part taking off those corroded nuts) and couldn't get the plug to plug up... after failing for a few minutes I thought to compare the old and new plugs and sure enough the config of the new plug was different. I should have bought the 234-9003. I even compared the pics on Amazon too, it's the sensor with fewer holes in it and the damn thing costs twice as much.

Oh well, at least I didn't damage the threads on the studs and once my new one comes in, should be a cinch to put in.

Thanks for all your helpful posts on this subject. Hopefully no one else will make the same silly mistake considering the wealth of knowledge available.

Question -- is yours an auto or a manual transmission? the 234-9003 is for the 5spd, correct? Are the plugs different at all between the auto/5spd or just the wire length? Mine is an auto to 5spd swap, now that the O2 sensors are bad I'm curious if i need to stick with auto plugs or go with 5spd'ers. FWIW the ECU in my truck has also been swapped over to the 5spd version.

 

[TheDurk]

Question -- is yours an auto or a manual transmission? the 234-9003 is for the 5spd, correct? Are the plugs different at all between the auto/5spd or just the wire length? Mine is an auto to 5spd swap, now that the O2 sensors are bad I'm curious if i need to stick with auto plugs or go with 5spd'ers. FWIW the ECU in my truck has also been swapped over to the 5spd version.

He has a 5sp. , but the plugs are the same between auto and 5speed. His problem was he bought an O2 for a Federal when he needed an A/F for aCali. (the 234-9003). The A/Fs all have the same plug, and the O2s all have a different one.

In your case, the only issue is wire length. The 5 speed is about 3.5 inches longer than the auto, so I would think yours would be stretched tight. The 5 speed would work either way, so I'd go with that. It's possible the auto harness is different, and maybe you don't need the extra length. If the installation you have looks normal, you might be able to use the auto sensor. Either one will plug up if the wire reaches, assuming you got the O2/AF part right.

The important thing is to be sure you if you have a one-cat (O2 in front) or a two-cat (A/F in front). Don't make the mistake he did and just guess.

Did you do the swap yourself? Because if the ECU swap included the harness all the way to the sensor, It's possible you have two cats on the exhaust and a one-cat ECU and harness. That would work, but you would need an O2 not an A/F. So maybe you should take a picture of the sensor plug and compare it to the Denso web site to be sure. That would also change the wire length needed, so you could measure that, too, and be sure.

Thinking over all the possibilities of how the swap was done, that's the best route. PO might have brought the sensors over from the donor, so you really have no idea what's in there if you bought it swapped.

 

[Pj Benn]

Looks to me like the problem is with sensor 1. An O2 sensor usually should read between .1 and 1 volts. .1 being a lean condition and 1 being rich

I am also working through a issue. Wrote out a detailed post and didn’t post. Here’s the short and sweet. I heard coolant temp sensor can cause rich condition too. Open loop if it thinks engine is still warming up. How can I test to see if it’s that sensor or the pre cat sensor that is causing the rich condition?

 

[Masaka]

Reporting back a small detail I learned after following Tim's video to change upstream O2 sensor (ahead of CAT) on non-CA limited.

I did NOT clear the CEL after putting in new sensor and wanted to see how long it takes the ECU to complete the tests on its own: CEL cleared about a mile in on the 3rd ride after replacing sensor. Both 1st and 2nd rides were about 15 miles each, mix of local and freeway. There was about 8 hours gap between 1st and 2nd ride, and 1 hour gap between 2nd and 3rd ride (during which the CEL cleared.) So ECU did pretty much a textbook 2-ride test to check O2 response time. Used Denso 234-4162 part from Amazon.

 

[Michael0789]

OK I KNOW THIS THREAD DIED BUT THIS NEEDS TO BE SAID . . .

my 99 sr5 v6 federal emissions is coding P0172 from time to time, bank 1 running rich. this can be very deceptive because there is no bank 2 O2 sensor. it could be that bank 1 IS rich. it could also be that bank 2 is rich also, but the ecu can't tell you that because there are no bank 2 oxy sensors. see what I mean?

so there is no A/F sensor in the sense of the ca regs. someone posted about watching the fuel trims and the oxy sensor together to see how they interplay. I can do that with scangage so that's next stop. maf not the problemo. this time. propane vacuum test next up.....

a look at the plugs is probably the fastest way to find out what the mixture is.

the more fun i have with the fvz and efi, the more i miss the straight 6 engines with carbs and distributers and push rods and low end torque and Smooth runnings.

is there any way to compute A/F for the 99 federal regs ? if i could just get that stinking number some how. I think i saw an after market A/F O2 sensor install in an exhaust manifold somewhere. any one do that?



ciao ciao

 

[Frankers]

Saw that there was already an O2 sensor post and so going to revive the tread.

I have a 99’ sr5 v6 cali with the upstream A/F and O2 downstream. Recently got the P0420 code and so I’m trying to figure out if it’s the downstream O2 sensor or the cat. Im not the first owner and so not sure when the sensors were last replaced. Took a look and noticed the current sensors are denso. The bolts look pretty rusty and I live over on the west coast (I think car had previously been in Pa.) and so I want to think that it’s been a while. What is the expected lifespan of a denso O2 sensor?

 

[JoeT4R]

Saw that there was already an O2 sensor post and so going to revive the tread.



I have a 99’ sr5 v6 cali with the upstream A/F and O2 downstream. Recently got the P0420 code and so I’m trying to figure out if it’s the downstream O2 sensor or the cat. Im not the first owner and so not sure when the sensors were last replaced. Took a look and noticed the current sensors are denso. The bolts look pretty rusty and I live over on the west coast (I think car had previously been in Pa.) and so I want to think that it’s been a while. What is the expected lifespan of a denso O2 sensor?

It could be the sensor or it could be the cat. I've lived with the P0420 for almost 10 years now. I've replaced my A/F ratio sensor twice and my o2 sensor once. Only adverse affects I've seen are an ugly orange light in my dashboard. It came complimentary with the truck when I bought it. I'd venture to say my issue might be the cat, but I don't want to bother with it. I'm very curious to see what your outcome will be.

As far as life expectancy of Denso sensors, I cannot say off the top of my head. My A/F ratio sensor has been replaced in 2015 and in 2021, both times I used oem Denso. Ymmv.

Sent from my SM-T220 using Tapatalk

 

[Jakubkubap]

Hey bumping this thread cause I can’t post my own.

But my bank 1 is acting as a downstream and bank 2 is acting as an upstream .

Bank one is steady between .5-.8 and bank 2 moves with throttle input.

Is my ob2 labeling it weird , I’m using OBDLink

 

[Robb235]

Hey bumping this thread cause I can’t post my own.

But my bank 1 is acting as a downstream and bank 2 is acting as an upstream .

Bank one is steady between .5-.8 and bank 2 moves with throttle input.

Is my ob2 labeling it weird , I’m using OBDLink

Can you post a screenshot? You should only have one bank, with sensor 1 (upstream) and sensor 2 (downstream). What year is your truck? I’m guessing ‘99 or newer.

 

[Jakubkubap]

Can you post a screenshot? You should only have one bank, with sensor 1 (upstream) and sensor 2 (downstream). What year is your truck? I’m guessing ‘99 or newer.

It is a 99 4x4 CA emissions, my CAT wont ready up and I think this is the issue.

The car has no codes or pending code. During smog it passed the sniffer and visual but failed for Readiness.

Funny thing is car idles and runs flawless.

So I think the 02 sensors got swapped by previous owner because my Sensor 1 is stead between .6 -.8 and bank 2 is hopping around like a afr guage based on throttle , honeslty this isnt make sense to me because it got swapped the narrow band sensor should vary alot more still.

Picture attached.

Thanks Robb

 

[Robb235]

It is a 99 4x4 CA emissions, my CAT wont ready up and I think this is the issue.

The car has no codes or pending code. During smog it passed the sniffer and visual but failed for Readiness.

Funny thing is car idles and runs flawless.

So I think the 02 sensors got swapped by previous owner because my Sensor 1 is stead between .6 -.8 and bank 2 is hopping around like a afr guage based on throttle , honeslty this isnt make sense to me because it got swapped the narrow band sensor should vary alot more still.

Picture attached.

Thanks Robb

Your front sensor is steady because you have an upstream “air fuel ratio sensor” and not the older style narrowband O2 sensor. The AFR sensor will not switch back and forth like an O2 sensor. Your downstream sensor is a narrowband O2 sensor. Sounds like it’s running normally. My guess is catalytic converter that’s not as efficient as the ECU requires.

 

[Jakubkubap]

Thank you , yea maybe it’s the cat. The car runs great. The thing that scratches my head it passes the sniffer test and also after around 1k miles no check engine.

Might try some Cataclean or something and see if it sets.

 

[Jakubkubap]

Your front sensor is steady because you have an upstream “air fuel ratio sensor” and not the older style narrowband O2 sensor. The AFR sensor will not switch back and forth like an O2 sensor. Your downstream sensor is a narrowband O2 sensor. Sounds like it’s running normally. My guess is catalytic converter that’s not as efficient as the ECU requires.

Also did your o2 simulator you have in your thread make your cat ready up ?

 

[Robb235]

Also did your o2 simulator you have in your thread make your cat ready up ?

Can’t remember if it passed the readiness monitor or not. I’m currently not running the $5 O2 simulator at the moment. Didn’t swap it over last time I replaced the downstream sensor.

 

[Jakubkubap]

Can’t remember if it passed the readiness monitor or not. I’m currently not running the $5 O2 simulator at the moment. Didn’t swap it over last time I replaced the downstream sensor.

I'll give a try and let you know if it works else ima try a new downstream.

Thank you for all the help.

 

[gamefreakgc]

I'll give a try and let you know if it works else ima try a new downstream.

Thank you for all the help.

The readiness indicators can take several hundred miles of driving before setting. I have one that never sets but I have a 98 and in CA it is allowed. They take very specific drive cycles that I never do to full set.