[BillG]

Ok timing belt, water pump all changed. So I got to run all my live data. I hope these results help point me in the direction to find the cause. Long Ft # 1 is -3.09% Long Ft # 2 is -0.81. Short Ft # 1 is -3.16% Short Ft # 2 is -0.03%. Total Ft # 1 is 1.01. Vapor pressure is-0.01 psi. O2 Ft B1 S2 and O2 Ft B2 S2 are 99.16%. O2s B1 S2 is .74v O2s B2 S2 is .70v.

You need to read the O2 B1S2/B2S2 values as voltages on a graph AFTER the engine has started to warm up. They should bounce between 0.1 and 0.9 volts. If they go/stay below 0.1 or above 0.9, they are bad or you have a wiring issue. If they bounce mostly below 0.5 constantly, your engine is probably running lean or your sensors are bad. If it's mostly above 0.5 (the likely scenario), your engine is running rich, your cats are ineffective, or your sensors are bad.

The ideal thing is to (if your scanner has this ability), capture the RPM and 2 sensor voltages (may as well capture short and long term fuel trims too). You should make sure the capture happens at a 1-second rate, if you have that ability. Then start the van, idle in part for 5 minutes, then go for a 10-20 minute drive at different speeds from in-town starts/stops to highway speeds. Grab your capture data and throw it on a spreadsheet graph.

 

[onewic22]

You need to read the O2 B1S2/B2S2 values as voltages on a graph AFTER the engine has started to warm up. They should bounce between 0.1 and 0.9 volts. If they go/stay below 0.1 or above 0.9, they are bad or you have a wiring issue. If they bounce mostly 0.5 constantly, your engine is probably running lean or your sensors are bad. If it's mostly above 0.5 (the likely scenario), your engine is running rich, your cats are ineffective, or your sensors are bad.

The ideal thing is to (if your scanner has this ability), capture the RPM and 2 sensor voltages (may as well capture short and long term fuel trims too). You should make sure the capture happens at a 1-second rate, if you have that ability. Then start the van, idle in part for 5 minutes, then go for a 10-20 minute drive at different speeds from in-town starts/stops to highway speeds. Grab your capture data and throw it on a spreadsheet graph.

 

[onewic22]

View attachment 60946

That’s 5 minutes of idle time for o2s b1 s2 and b2 s2

 

[onewic22]

 

[onewic22]

View attachment 60947
View attachment 60948

Some stop and go travels

 

[onewic22]

Some stop and go travels

How do I test the original oxygen sensors with an ohm meter

 

[onewic22]

How do I test the original oxygen sensors with an ohm meter

And what should the readings be

 

[onewic22]

 

[onewic22]

View attachment 60950

Idle after nice drive.

 

[onewic22]

Idle after nice drive.

 

[onewic22]

View attachment 60951

Highway driving

 

[BillG]

Ugh! I keep wanting to clean the smudge off the lens when looking at these!

Some clarification required just so I'm sure I'm reading them correctly... The first photo (5 mins of idle time) seems to indicate a problem (with Bank 2) if it's AFTER 5 minutes of idle time but I'm confused. I assume the bottom (x-axis) is seconds. The graph starts at 1240, which almost 21 minutes. However, it ends at 1420, which is 180 seconds (3 minutes) after the start. So, was it a graph after 5 minutes of idling time (plus 15 mins of setting the tool up) or was this misstated and it's actually 3 minutes of idle time right from the starting of the car? If this is time zero (cold start) through 3 minutes, then this graph can be ignored entirely, because the sensors need to heat up before they can be read

For the next 2 pics (stop and go travels) This is where the RPM graph would be helpful to be sure, but it seems to indicate an issue. In theory, both banks should be doing approximately the same thing at the same time. It's not a perfect match, but, both graphs should move roughly the same direction to roughly the same voltage at roughly the same time when RPMs change up or down. The sensors look like they're going opposite directions sometimes, but it seems like B2 is spending a lot more time low and is less responsive, which makes me thing that sensor itself is "lazy". However, there is a big caveat here. It looks like this as immediately after the previous pic, based on the time graph. If so, it's possible, if the van still wasn't warmed up, that the sensors are still reading erroneously. The fact that they drop down seemingly to 0V (supposed to stay between 0.1 and 0.9), says that maybe this is the case.

The idle after a nice drive starts to show some indication that maybe bank 1 is less efficient (either combustion or catalyst) than it should be. It's bouncing around above the half way point (0.5V). Then, in the highway drive, the graph once again seems to show B2 moving differently than B1, but both sensors once again drop down to 0V and both are swinging wildly, which I wouldn't expect at typical highway driving (consistent speed/RPM).

With all this, I can say that, to me, it looks like you might have multiple issues. If you didn't use genuine Denso (or Toyota) branded post-cat O2 sensors in your parts cannon, I would suspect definitely the B2S2 sensor (seems lazy; drops to 0V sometimes) but B1S2 might also have an issue (it also dropped to 0V sometimes) depending on which bank was "right" based on RPMs/speed. I would also suspect that maybe you have a combustion issue (or your cats are inefficient; less likely because you said they were new) and the ECU is compensating almost enough but not quite, which causes the codes.

 

[BillG]

BTW, the "idle after a nice drive" B1S1 is the kind of graph I would expect if you're idling in the driveway in park after a fully warmed drive cycle, except that it's too high (hanging around 0.7V), which indicates poor combustion (too much unburned HCs).

 

[onewic22]

Ugh! I keep wanting to clean the smudge off the lens when looking at these!

Some clarification required just so I'm sure I'm reading them correctly... The first photo (5 mins of idle time) seems to indicate a problem (with Bank 2) if it's AFTER 5 minutes of idle time but I'm confused. I assume the bottom (x-axis) is seconds. The graph starts at 1240, which almost 21 minutes. However, it ends at 1420, which is 180 seconds (3 minutes) after the start. So, was it a graph after 5 minutes of idling time (plus 15 mins of setting the tool up) or was this misstated and it's actually 3 minutes of idle time right from the starting of the car? If this is time zero (cold start) through 3 minutes, then this graph can be ignored entirely, because the sensors need to heat up before they can be read

For the next 2 pics (stop and go travels) This is where the RPM graph would be helpful to be sure, but it seems to indicate an issue. In theory, both banks should be doing approximately the same thing at the same time. It's not a perfect match, but, both graphs should move roughly the same direction to roughly the same voltage at roughly the same time when RPMs change up or down. The sensors look like they're going opposite directions sometimes, but it seems like B2 is spending a lot more time low and is less responsive, which makes me thing that sensor itself is "lazy". However, there is a big caveat here. It looks like this as immediately after the previous pic, based on the time graph. If so, it's possible, if the van still wasn't warmed up, that the sensors are still reading erroneously. The fact that they drop down seemingly to 0V (supposed to stay between 0.1 and 0.9), says that maybe this is the case.

The idle after a nice drive starts to show some indication that maybe bank 1 is less efficient (either combustion or catalyst) than it should be. It's bouncing around above the half way point (0.5V). Then, in the highway drive, the graph once again seems to show B2 moving differently than B1, but both sensors once again drop down to 0V and both are swinging wildly, which I wouldn't expect at typical highway driving (consistent speed/RPM).

With all this, I can say that, to me, it looks like you might have multiple issues. If you didn't use genuine Denso (or Toyota) branded post-cat O2 sensors in your parts cannon, I would suspect definitely the B2S2 sensor (seems lazy; drops to 0V sometimes) but B1S2 might also have an issue (it also dropped to 0V sometimes) depending on which bank was "right" based on RPMs/speed. I would also suspect that maybe you have a combustion issue (or your cats are inefficient; less likely because you said they were new) and the ECU is compensating almost enough but not quite, which causes the codes.

mine goes by seconds. I will do beter test today

 

[BillG]

If you have the ability to save the data in a csv file (or some such), you can capture a log file of LTFTs, STFTs, RPM, vehicle speed, ambient temp, coolant temp, O2 voltages, maybe the air/fuel ratio, and timing values, etc. Basically, you turn it on to capture everything and then you can analyze what you've got on side-by-side graphs. If you're limited to whatever the scan tool shows and then have to take a photo of that, obviously, that makes things harder to save ALL data. However, the way around this is to try to figure out A thing that's wrong, resolve that and then move on to the next thing. Ideally, you would have captured this data FIRST before throwing all your parts at the problem. It could be something like your bad timing belt threw off the timing and now all your misc. replaced parts are sub-optimal (as compared to factory originals) and you'll be chasing problems forever. Personally, I would throw the 2 downstream O2 sensors back in (should be quick and easy, assuming you used a high-quality anti-seize compound on the threads) and see what the graphs look like then. Better still, go for a long drive and watch the values, let it cool, swap the original sensors in and then repeat the process. I might also swap the original MAF back in too.

 

[onewic22]

If you have the ability to save the data in a csv file (or some such), you can capture a log file of LTFTs, STFTs, RPM, vehicle speed, ambient temp, coolant temp, O2 voltages, maybe the air/fuel ratio, and timing values, etc. Basically, you turn it on to capture everything and then you can analyze what you've got on side-by-side graphs. If you're limited to whatever the scan tool shows and then have to take a photo of that, obviously, that makes things harder to save ALL data. However, the way around this is to try to figure out A thing that's wrong, resolve that and then move on to the next thing. Ideally, you would have captured this data FIRST before throwing all your parts at the problem. It could be something like your bad timing belt threw off the timing and now all your misc. replaced parts are sub-optimal (as compared to factory originals) and you'll be chasing problems forever. Personally, I would throw the 2 downstream O2 sensors back in (should be quick and easy, assuming you used a high-quality anti-seize compound on the threads) and see what the graphs look like then. Better still, go for a long drive and watch the values, let it cool, swap the original sensors in and then repeat the process. I might also swap the original MAF back in too.

So which o2 sensor cause p0420 code. Up or down stream sensor

 

[BillG]

P0420 indicates a bank 1 problem. There are 2 sensors on each bank. Sensor 1 (upstream; aka, pre-cat) is an Air/Fuel sensor. It's like an O2 sensor, but different. It provides feedback to the ECU along with the data from the MAF to attempt to keep the A/F ratio at precisely 14.7. Sensor 2 (downstream; aka, post-cat) is the O2 sensor operates based on the idea that, if you put an optimum air/fuel mix into the cylinders, you will get a certain amount of unburned fuel into the exhaust and, if the cat is working properly, will get a minimal amount of uncatalyzed hydrocarbons into the post-cat exhaust. The only mechanism for triggering a P0420 would be Bank 1/Sensor 2 (aka, downstream) O2 sensor. It should be (I think) Denso 234-4516 for FWD and 234-4515 for AWD. All that said, as is typical, it makes the assumption that you're putting the "correct" amount of unburned hydrocarbons into the exhaust manifold, which gets routed into the cat. If the engine is running rich from something like a leaky injector and sending raw gas in or its running lean from something like a compressed intake manifold gasket and causing incomplete combustion, the cat can fail to fully catalyze the HCs and trigger a code.

 

[cougarhound]

I don't know. It looks like bank 1 sensor 2 has the bad cat. It is going up and down when it should be steady. There are illegal ways to deal with this btw. Maybe just buy an aftermarket cat with a 3 year warranty? If you already changed the cat then replace the O2 sensor with a Denso. I wouldn't bypass the cats...Carbon monoxide is deadly. Especially with a minivan that might carry children or pregnant women. Get it running right!

 

[Therbi]

I get that a cat reduces CO emissions, but thats a bit of a stretch saying a cat delete is deadly to people inside the car dont ya think.

 

[cougarhound]

I get that a cat reduces CO emissions, but thats a bit of a stretch saying a cat delete is deadly to people inside the car dont ya think.

Yea but I'd rather not have that on my conscience. I definitely wouldn't want my kids sleeping in a car with a cat delete. I do have a carbon monoxide detector in my 4runner when I took it on a road trip to Alaska.