Hoping for some guidance.

The back story so far..

For the past couple of months I have been getting the P0420 code on Bank1 sensor 2, with the code appearing at the 150 mile mark.

No obvious leaks, and as I have just put a resistor on Bank 2 sensor 1, I thought perhaps it has to be the Bank 1 sensor 2 that has developed a fault... as with my luck things go together! Hoping it is not the cat.

I currently have a Toyosport manifold and Proflow exhaust fitted, with this problem appearing shortly after installation, but as stated above, no obvious leaks and no rattles from the cat or anywhere else.

Using the torque app and OBD11 I have watched all three sensors, re: voltage and fuel trim, with the following average results (keeping it brief);

Bank 2 sensor 1 - voltage varies as does fuel trim at various revs.

Bank 1 sensor 1 - voltage varies as does fuel trim until 2000 revs and cruising, then the voltage drops to 0 and fuel trim sticks at 19.5.

Bank 1 sensor 2 - voltage varies from 0.8-0.9 constant and fuel trim seems to stick at the -100.8 but eventually does move a little.

Put another Bank 1 sensor 2 in... this shows the same results as my original sensor (as above).

Excuse my ignorance, but is this normal for Bank 1 sensor 1?

And, infact what is normal for all sensors?

I have read various posts on various sites, trying to understand and resolve the P0420 code problem. Some have suggested adding an extension to the sensor, but I want to locate and resolve the problem, as to me that is just masking it... well if that works.

Advice and guidance greatly appreciated.

Dear Deviant

Can you revisit and edit your post for clarity.
You have bank 1 sensor 1 twice.

I think I know what you mean, but just to be sure.

You say you put another bank 1 sensor 2 in. Is that a new sensor?
B1 S2 is measuring the efficiency of the cat. If both reading the same. Suggests senors are working and reporting back the CAT is not well.

The 100.8 reading is not right.

Are the values provided when engine is properly up to temp?

Edit.
Do you have access to a multi meter?

The fuel trims will never read over (+/-) 30ish without a "too rich" or "too lean" code. So that's a bogus reading. 

Voltage of 0.8/0.9 means "rich". In your case probably "very rich". No telling how rich. Just, at the max of richer than stoichiometric that the narrowband can measure. 

I hate resistor "fixes" with a passion so it could have something to do with that. 

Long term fuel trims should be 0 with a tolerance each way of about 7ish. Short term will swing back and forth.

Could be cat, could be leak, could be o2 sensors.

Quote from: Ardent on July 10, 2019, 21:20Dear Deviant

Can you revisit and edit your post for clarity.
You have bank 1 sensor 1 twice.

I think I know what you mean, but just to be sure.

You say you put another bank 1 sensor 2 in. Is that a new sensor?
B1 S2 is measuring the efficiency of the cat. If both reading the same. Suggests senors are working and reporting back the CAT is not well.

The 100.8 reading is not right.

Are the values provided when engine is properly up to temp?

Edit.
Do you have access to a multi meter?

Yes the values are at the proper temp, and the sensor was changed over from another MR2.

Yes I have a multimeter.

This post might be worth a look to rule in or out the sensors. Open the attached pic.

https://www.mr2roc.org/forum/index.php?msg=799752

Quote from: Ardent on July 10, 2019, 23:30This post might be worth a look to rule in or out the sensors. Open the attached pic.

https://www.mr2roc.org/forum/index.php?msg=799752

Thank you, will check.

Your welcome

Thats the way we roll.

Which reminds me, need to check mine as I have some readings very similar to yours.

The torque pro is good is see things in real time. I usually go for a needle view but the graph view as uggested by some one helps with viewing the sensors. I would say my B1 S2 is lazy at best.

Checked finally between the rain:

2,1 = 17.2
1,1 = 9.2
1,2 = 16.5

All marginally out of spec then.
But not complete crazy out.

Perhaps
Clear fault, have a drive. Set torque pro to display and record. Review over a cuppa?
See what they are doing once up to temp.

Issue could be elsewhere, worth checking for leaks before getting new sensors.

I would say they're all in need of replacement.

@deviantmr-s

Have pm'd you a link that may be helpful.

Might be worth double checking for any leaks as the other options are likely to invole wine tokens.
Leak detection spray? or the tissue on some long nose pliers.

I previously had leaks, never knew until exhaust stripped down for other reasons.

Quote from: Ardent on July 14, 2019, 16:54@deviantmr-s

Have pm'd you a link that may be helpful.

Might be worth double checking for any leaks as the other options are likely to invole wine tokens.
Leak detection spray? or the tissue on some long nose pliers.

I previously had leaks, never knew until exhaust stripped down for other reasons.

Will do, received thank you.

Just to add to this (found thread while researching) ive just had EML and same PO420 code come up after a long thrash down motorway at weekend, reset code with Torque app and it was fine for a few days including day on track and the return journey but EML and code came on again yesterday, i had forgotten about until then!

Was a little concerned it was my new cats2u cat fitted a few weeks ago but i checked post cat sensor output in Torque app and voltage is all over the place!, sometimes its ok but others it does very little so looks like the sensor has had its day to me, its been in and out a few times over past month swapping exhaust bits around so that wont of helped so ive just ordered a new Denso DOX-0206 from sparkplugs.co.uk after finding info on here , will get that fired in and see how we go, cat is still under warranty if it is the problem but i dont think so.

Ian

Sounds like my sensor.
Sporadic.

Fitted the new Denso post cat sensor today and readings look a lot better on torque app and not so lazy, however after a 10mile testdrive I scanned for error codes and the PO420 is back!... I did clear it after fitting new sensor but will run it for a few days see if it comes back again, i will also try and get local garage to t=do me a Mot emissions check to see what that reveals!

If its cat failed i will have to see just how good this warranty is they offer, i suspect they will find a loophole to get out of it but we will see, bit annoyed as its done less than 1000miles

Ian

Double check for leaks. From engine to cat

Quote from: shnazzle on July 20, 2019, 14:28Double check for leaks. From engine to cat

I think for first time in awhile since I fitted this cat im leak free but will check it all again, i struggled with leaks at the 3amigos with oe cat but now it seems ok, weirdly with the leak at 3amigos flange I never had any error codes, but they were very small only I could hear it at low revs in town etc but once removed you could see where it had been getting past the fire ring gasket.  I think its the cat personally but we will see.

Were the ring gaskets cats2u or Mr Ts?

Quote from: thetyrant on July 20, 2019, 15:28

Quote from: shnazzle on July 20, 2019, 14:28Double check for leaks. From engine to cat

I think for first time in awhile since I fitted this cat im leak free but will check it all again, i struggled with leaks at the 3amigos with oe cat but now it seems ok, weirdly with the leak at 3amigos flange I never had any error codes, but they were very small only I could hear it at low revs in town etc but once removed you could see where it had been getting past the fire ring gasket.  I think its the cat personally but we will see.

It could absolutely be your cat. No doubt. That is what that code is for. But, just to isolate that it is indeed the cat. Tis free!

Quote from: Ardent on July 20, 2019, 15:39Were the ring gaskets cats2u or Mr Ts?

Ive had both types over past months when ive been changing parts about, currently on the cats2u ones which I know people don't rate but I think that's because they are not a perfect fit as supplied but people just force them in anyhows which i did on first set and they leaked quite quickly,  next set I found that if modified them slightly the fit and seal perfectly and no signs of leaks in nearly 1000miles and 2 track events, the first set I just fitted without modding hoping them would compress to shape as they are slightly too large on outer diameter but they get deformed when you nip up the 3amigos, no doubt why people are having problems with them i think, I then went for MrT when I tried a used oe cat pipe which were straight fit no issues, but when I fitted this new cat I used another set of cat2u rings and shaved high spots off outer edge so they fitted neatly into the recess and they have been perfect and no leaks, been over full exhaust again yesterday checking for leaks and nothing, im hyper sensitive to hearing exhaust leaks but also used the tissue in pliers to check for air movement and nothing.

Will get it on the mot tester see what emissions are, reading the warranty advice pamphlet that came with new cat if i get this is should help identify if its cat and help with claim if it is.

I thought i was done with this after faffing about with used cats and then having flexi issues so just bought a new one hoping that was last of it, seems not!

Checked mine today.
2 min job even for me.
Spec is 11 - 16 @ 20c
Well in spec at 15.9

Though most of the things have been mentioned, let`s see if anything is missed.
According to the manual, the P0420 trigger is: After engine and catalyst are warmed up, and while vehicle is driven within set vehicle and engine speed range, waveforms of oxygen sensors (bank 1 sensor 1 and bank 1 sensor 2) have same amplitude (2 trip detection logic). Which if accurate, narrows the problem down to two sensors. However, I kind of doubt based on their troubleshooting guidelines.

1. Check for air leaks. Especially, since you have a new catalyst, the cat itself should be the last resort.
2. Check oxygen sensor resistance. This is one health status indication, but unfortunately does not guarrantee proper dynamic response, that we care of.
3. Use Torque. One of the important things is to ensure ECM has completed oxygen and catalyst control routines. To do so, use the DTC display and check the status. You will be surprised, how long it might take to complete them, even if you drive it daily...
4. Do the Toyota troubleshooting. Again use torque, but this time remove every display and graph apart from the voltage of the three oxygen sensors (the latter to ensure maximum refresh rate). As per MrT procedure:
(a) In our case use Torque to monitor the three voltages.
(b) Start the engine and warm it up with all the accessories switched OFF until water temperature is stable.
(c) Race the engine at 2,500 – 3,000 rpm for about 3 min.
(d) After confirming that the waveforms of the heated oxygen sensor (bank 1, 2 sensor 1 (OX1A, OX2A)), oscillate around 0.5 V during feedback to the ECM (at a constanst engine speed of about 2500-3000rpm), check the waveform of the heated oxygen sensor (bank 1 sensor 2 (OX1B)). If there is a malfunction in the system, the waveform of the heated oxygen sensor (bank 1 sensor 2 (OX1B)), is almost the same as that of the heated oxygen sensor (bank1, 2 sensor 1  OX1A, OX2A)).
So you would expect a slower response rate on the post-cat sensor.
Hopefully, the above will help narrow the problem down.

Well played Sir/Madam

That is a spot on post for someone with 12 posts. Someone has been busy reading or comes with a solid knowledge foundation. Either way, well played.

Quote from: Ardent on July 22, 2019, 23:17Well played Sir/Madam

That is a spot on post for someone with 12 posts. Someone has been busy reading or comes with a solid knowledge foundation. Either way, well played.

+1.  I reckon I'll be reading this again.... ;-)

Quote from: potge on July 22, 2019, 22:282. Check oxygen sensor resistance. This is one health status indication, but unfortunately does not guarrantee proper dynamic response, that we care of.

Question about this though. I've heard of measuring the heater cct. I've checked the sensor wires themselves out of curiosity & got high M-Ohms...open circuit really. ?