P0420 coming back after new Cat and o2 sensors (1 Viewer)

[Gamecocks910]

hmm dont order anything..make sure you go through the video's these codes are very common.. but also a pita to troubleshoot your first time doing it. But sometimes you learn by dipping your foot into the fire..

btw the O2 sensors you got were original Denso ones right? cause toyo's are very particular on having Denso O2 sensors. Original Denso O2's.

Ah good call. Yes they were densos. Full transparency I did order from amazon. They were all in denso boxes, stamped, etc.

 

[Gamecocks910]

Well thank you @BnvS and @jerryb - Those videos did help me understand the "system" a little better. Man I went down a youtube rabbit hole.

Taking into consideration what I learned and some of the results seen in the video, It appears all o2 sensors are reading properly except for Bank1, sensor 2. That would make align with the P0420 code that I have been seeing.

But to everyone's point, what is causing that? That is still undetermined as of right now. Could it be the sensor or is the new cat not working properly? I will try and determine that next. I was trying to pull that o2 sensor to swap out with Bank 2 but as it is loosening, it becomes tighter. I am nervous that I might snap the stud so I might have to take it into a shop in case the stud does in fact snap. I don't have the skill or tools to retap the stud....

Could be related but could also be unrelated, @2001LC, I noticed in one of your threads, replacing the fuel pumped helped solve for a 420 code. Was that the case? I was having some issues with prolonged starts (happened again this AM) which could be a factor in both scenarios. I would assume?

 

[jerryb]

I have tried in the past to log oxygen storage time delay with only tech stream to really find out if the cat is working.
To me this is almost the definitive test. TS works in the graphing of all 4, but time is the issue.
I do not have a 4 channel scope. Nor do I believe anyone I would take a car to for that specific purpose would bother when you account for the time it would take to fish out the ecu and get at all 4 wires output compared to time to replace either a cat, or an o2 sensor.
I've also dumped MAP gas in the airbox to check full rich in the driveway.
All these little tests take you even further down a hole.
In the end a 400 weld up cat job cats you a few years, if that's better than spending a ton of time there's nothing wrong with going that way.


you would get a check engine light rich or lean before a cat code. On paper at least because that should be an immediate code.
Assuming all else is good..
if you watch or graph you front sensor voltage at full throttle you will know if your pump is supplying appropriate amounts of fuel.
That in itself is not a 100% promise that a fuel pump is working as advertised. Heat, resistance, age of pump, injector condition, leaks, etc all factor in.

 

[2001LC]

Well thank you @BnvS and @jerryb - Those videos did help me understand the "system" a little better. Man I went down a youtube rabbit hole.

Taking into consideration what I learned and some of the results seen in the video, It appears all o2 sensors are reading properly except for Bank1, sensor 2. That would make align with the P0420 code that I have been seeing.

But to everyone's point, what is causing that? That is still undetermined as of right now. Could it be the sensor or is the new cat not working properly? I will try and determine that next. I was trying to pull that o2 sensor to swap out with Bank 2 but as it is loosening, it becomes tighter. I am nervous that I might snap the stud so I might have to take it into a shop in case the stud does in fact snap. I don't have the skill or tools to retap the stud....

Could be related but could also be unrelated, @2001LC, I noticed in one of your threads, replacing the fuel pumped helped solve for a 420 code. Was that the case? I was having some issues with prolonged starts (happened again this AM) which could be a factor in both scenarios. I would assume?

I don't recall a post where fuel pump fixed a P0420. Link me to it, if you find it.

But I did have a VVT engine (2006-07) with P0171 & P0174 (BK1 & BK 2 lean DTCs). I'd not likely have seen the DTC, had I not had scanner hooked in at the time it happen. Which fuel pump replacement solved. 2006-07 have a buggy fuel pump. What happens is they get hot in high speed mode. Which it runs in high speed mode, when engine RPM high. Which heat increase electric current resistance. Then, as RPMs drop back, fuel pump power switch to low speed (slowing pump) mode. Pump at this point fails to deliver enough fuel flow/pressure.

Long crank to start "prolonged starts". Provided engine is well tuned. Is most often associated with fuel injector leak down. This is most noticeable in cold engine, but when warm up. Then shut down and re-started it starts fine/fast.

FSM has a few test for this. First is done with fuel pressure gauge. If it fails that test. Then pull all injectors and do fuel injector leakage test on each. Any fail, I'd then send all 8 Fuel injectors out to have tested, cleaned and rebuilt.

When to Clean or Replace fuel injectors

Please post your experiences and thoughts on the subject. I’ve been considering cleaning or even replacing all 8 fuel injectors, is this wasting time and money. I understand keeping fuel injector clean by adding a can of additive to the gas tank, now & then, is a good practice. This keeps them...

forum.ih8mud.com

 

[BnvS]

@Gamecocks910 with 300k miles on the LC it doesn't hurt to getting your fuel pressure tested to see how your fuel pump is performing.

You can get a banjo adapter to hook on to your fuel line to get the fuel pressure. Search up how to do that as I am sure folks have posted the procedure on here.

The tester you can rent at Autozone.

Btw one way to make sure even before you check is to see if both ltft and stft follow each other up > +15% (in your case it's probably higher) . Do that at a few speeds. If you see the trims follow each other up then for sure check the fuel pressure.

 

[Gamecocks910]

Doubt anyone is following along anymore but after doing a little more troubleshooting and testing, I was still confused/stuck. Tough to devote a ton of diag time with a 1 year old and slinging software on the weekdays. I made an appt with a Lexus/Toyota Indy and was planning on dropping off this week.

Well I had to drive about 20-25 miles and thought of a post @2001LC made a few times about running at higher RPM for a few minute sprints and did something similar. Drove it pretty hard over the drive and tried to maintain 3500-4500 RPM throughout.

Well the CEL light went off on its own. Now is it fixed and will the light remain off....No, probably not. But at least I dont have to look at the CEL. I ended up cancelling the appt but will probably reschedule as I want to figure out why I got the light in the first place..

 

[2001LC]

Doubt anyone is following along anymore but after doing a little more troubleshooting and testing, I was still confused/stuck. Tough to devote a ton of diag time with a 1 year old and slinging software on the weekdays. I made an appt with a Lexus/Toyota Indy and was planning on dropping off this week.

Well I had to drive about 20-25 miles and thought of a post @2001LC made a few times about running at higher RPM for a few minute sprints and did something similar. Drove it pretty hard over the drive and tried to maintain 3500-4500 RPM throughout.

Well the CEL light went off on its own. Now is it fixed and will the light remain off....No, probably not. But at least I dont have to look at the CEL. I ended up cancelling the appt but will probably reschedule as I want to figure out why I got the light in the first place..

So the HIGH RPM run, correcting (CEL no long on), points to a few possibles.
In need of a good tune.
Prolonged idling
Frequent short and slow drives from a cold start, and not getting to HWY speeds.
A compression issue.
Bad gas.

I'd: Tune, Oil & filters, put 2 cans of 44K in a full tank of gas. Avoid idling and short slow drives from a cold start. Do frequent HIGH RPM runs. If spark plugs have not been changed, change them for a good set (watch out for China boot leg junk). Do a compression test while, at start of spark plugs job. Also re boot & seal coils on spark plug (COP).

 

[Gamecocks910]

So the HIGH RPM run, correcting (CEL no long on), points to a few possibles.
In need of a good tune.
Prolonged idling
Frequent short and slow drives from a cold start, and not getting to HWY speeds.
A compression issue.
Bad gas.

I'd: Tune, Oil & filters, put 2 cans of 44K in a full tank of gas. Avoid idling and short slow drives from a cold start. Do frequent HIGH RPM runs. If spark plugs have not been changed, change them for a good set (watch out for China boot leg junk). Do a compression test while, at start of spark plugs job. Also re boot & seal coils on spark plug (COP).

Well I’m very guilty of 2 of those. My commute is 2.2 miles to my office and daycare is another 2 miles away. Do that a few times a day. I’ve noticed it sometimes won’t even get to operating temp on my commute.

Also, these past few months, I’ve started the car a good 10 min before I left the house. Didn’t want my 1 year old to be cold . I will stop doing this.

Note to derail the main issue but 2 questions. What to-do items are in your tuneup list? And second, what oil flavor Is your recommendation? (Ive been running mobile 1 syn high mileage)

 

[2001LC]

Look in my master thread and read some of my restore projects. But basically a tune is coolant service, spark plugs, coil boots, vacuum lines, filters, t-body clean, MAF clean and anything not to spec on engine.

Get the HM (High mileage) oil out. ASAP. Two 5K miles oil changes in a row, and will be hooked for life. Just use Mobil 1 5W-30 or it's upper shelve Mobil 1 EP (extended performance) Annual projection.

 

[landarcht]

My 2005 currently has 180K miles and have had the P430 code for over a year now. Replaced two passenger side O2 sensors with Denso, P430 no longer reads, but now instead throwing the O2 sensor code. In a separate post, I'm thinking of just splurge and get a Toyota factory OEM Cat. I'm also thinking of putting the factory air box back instead of the K&N intake that I've had on my rig for about 7 years, although nothing's wrong and MAF is squeaky clean last time I checked.