Help Passing Emissions on a Toyota Van?

[Losiracer2]

Idk if this is the right place to post this since its not CB7 related, but here goes...

My Moms got a 03' Toyota Sienna, 1MZ-FE engine. Its throwing code P0420 I think is Catalyst Bank 1 it says. I tried resetting the codes and going to the emissions testing place but they said that the OBD system wasn't "ready" yet.

This car is pretty damn confusing since it's got 3 O2 sensors and 3 catalytic converters. And that P0420 code doesn't really specify what's wrong, just tells you catalyst. So you think its the O2 sensors? or the Cats going bad?

An O2 sensor is about 180 bucks for a Denso one, Cats from Toyota are Hundreds of dollars.

If I knew which cat to replace I'd do it, but I'm kinda confused as to which one its saying is possibly bad. I don't want to have her spend a couple hundred bucks and the problem still persists.

Any ideas? Anyone work on the 1MZ-FE engines and had a similar instance happen?

[s2cmpugh]

I'm guessing that van has a V6 in it. If so, Toyota probably employed "pre-cats" for each cylinder bank followed by a final cat. converter after those. So it would basically be..manifold...pre-cat...(on both sides of the engine)...exhaust comes together from both sides then it goes thru another cat and on out the back. Or it could be a total of 4 O2 sensors which would yield 4 total cats. Two cats and two O2 sensors for each cyclinder bank.

For the O2 (yota calls them air/fuel senors) sensors; there is one sensor BEFORE the pre-cat for each cylinder bank and one or more sensors AFTER the exhaust gases come together (if they do) from each bank and go thru the final cat. The computer takes readings from those sensors and then compares the first O2 (before pre-cat) reading to the second O2 reading (final cat). It normally should fall in a predetermined range indicating the cat. is operating at the proper effeciency. If the readings begin to fall outside that range, then cat. effeciency OR the A/F sensor is failing resulting in a fault code.

You need to find yourself a "live" code scanner that can display readings of the O2 sensors as the car is running. This will help determine if the cats are losing effeciency or the sensors are getting old and lazy. You might be able to rent one of these, or purchase one online for around $130 or so??

I did a quick search and the repairs for this code range from O2 sensors, to cat. converters, and on to ECU replacement (software update, but the that ECU is NOT flashable so replacement is necessary).

The only way to prevent issues like these is to have full and complete combustion (good spark plugs, good gas, good PCV system, and a clean air filter) and making sure the O2 sensors are operating as prescribed. Some nissan Maximas are known for this too and those guys ended up having to replace their cats. My dad has a 2002 Camry with the same issue, but on a 4 banger. He replaced ALL the O2 sensors (which yota calls A/F sensors) and a coolant temperature sensor, but guess what? CEL came back and after I mentioned the cat. effeciency thing he basically said "F that, it runs good as it is and I don't have to do emmissions". Different in your case I know.

If you want to fix it yourself, I'd try to score that live code scanner to get exact readings from the sensors. Try to find the correct parameters for the sensors and then diagnose which one is having the issue. I'm not aware of a way to determine if it's the pre-cat or final cat, but maybe talking to a yota tech will help on that.

Hope this helps!

[Losiracer2]

I'm guessing that van has a V6 in it. If so, Toyota probably employed "pre-cats" for each cylinder bank followed by a final cat. converter after those. So it would basically be..manifold...pre-cat...(on both sides of the engine)...exhaust comes together from both sides then it goes thru another cat and on out the back. Or it could be a total of 4 O2 sensors which would yield 4 total cats. Two cats and two O2 sensors for each cyclinder bank.

For the O2 (yota calls them air/fuel senors) sensors; there is one sensor BEFORE the pre-cat for each cylinder bank and one or more sensors AFTER the exhaust gases come together (if they do) from each bank and go thru the final cat. The computer takes readings from those sensors and then compares the first O2 (before pre-cat) reading to the second O2 reading (final cat). It normally should fall in a predetermined range indicating the cat. is operating at the proper effeciency. If the readings begin to fall outside that range, then cat. effeciency OR the A/F sensor is failing resulting in a fault code.

You need to find yourself a "live" code scanner that can display readings of the O2 sensors as the car is running. This will help determine if the cats are losing effeciency or the sensors are getting old and lazy. You might be able to rent one of these, or purchase one online for around $130 or so??

I did a quick search and the repairs for this code range from O2 sensors, to cat. converters, and on to ECU replacement (software update, but the that ECU is NOT flashable so replacement is necessary).

The only way to prevent issues like these is to have full and complete combustion (good spark plugs, good gas, good PCV system, and a clean air filter) and making sure the O2 sensors are operating as prescribed. Some nissan Maximas are known for this too and those guys ended up having to replace their cats. My dad has a 2002 Camry with the same issue, but on a 4 banger. He replaced ALL the O2 sensors (which yota calls A/F sensors) and a coolant temperature sensor, but guess what? CEL came back and after I mentioned the cat. effeciency thing he basically said "F that, it runs good as it is and I don't have to do emmissions". Different in your case I know.

If you want to fix it yourself, I'd try to score that live code scanner to get exact readings from the sensors. Try to find the correct parameters for the sensors and then diagnose which one is having the issue. I'm not aware of a way to determine if it's the pre-cat or final cat, but maybe talking to a yota tech will help on that.

Hope this helps!

Thanks for the tips! Yeah this van has 190k on it, mostly highway. I recommended that she replace all the O2 sensors since they're probably worn from use as a first step to try to eliminate the codes since a new cat for this car is outrageous.

I'll see if I know anyone that has a code scanner as you suggested and try that out.

[s2cmpugh]

No problem and I hope it helps! Cats are DAMN expensive now, especially if you have mutliple ones. Replacing those sensors will definately help to prevent this from occuring again.

I think amazon has some of those live code scanners for sale that are somewhat affordable. After you replace the sensors, I think the car needs 3 drive cycles (maybe more) to make sure all systems are running and ready. After that, check the codes again and see if any "pre-codes" exist. Those are basically fault codes that haven't been fully identified enough to warrant a CEL.

Good luck!

[red07frontier]

Replacing the 02 sensors will not fix it. They have specific codes if they were bad. The code you have is telling you the pre-cat on bank 1 is faulty. Thats the cat thats close to the manifold on the side that has cyl 1 on it. Thats bank 1. The 02 sensors are working because they are monitoring the flow through the cats. If it was the back post cat it would say cat efficiency but not bank one or bank 2.

[Losiracer2]

Replacing the 02 sensors will not fix it. They have specific codes if they were bad. The code you have is telling you the pre-cat on bank 1 is faulty. Thats the cat thats close to the manifold on the side that has cyl 1 on it. Thats bank 1. The 02 sensors are working because they are monitoring the flow through the cats. If it was the back post cat it would say cat efficiency but not bank one or bank 2.

I'm going to go the cheaper easier route first since they're long overdue for replacement anyways. Plus I've seen at least 4 other documented cases on the web of people having success with just doing the sensors with about the same mileage that's on this van. I just bought all Denso sensors from Rockauto last night so I should know in a few days once they're installed if it did solve the problem.

['93CB7Ex]

since you reset the pcm has the cel came back on?

also, obdii has readiness monitors. thats what they check when you go to emissions. just drive it around under all kinds of conditions and let the pcm run the tests and see if it comes back.

[Losiracer2]

since you reset the pcm has the cel came back on?

also, obdii has readiness monitors. thats what they check when you go to emissions. just drive it around under all kinds of conditions and let the pcm run the tests and see if it comes back.

yeah I couldn't pass emissions a couple days back because of that drive cycle, so I researched what it actually was for the car and did it last night. Midway between the 2nd drive cycle the lights came on after about 7 miles of driving on the highway. So I don't think there's a way of beating the system

['93CB7Ex]

did you check the codes? is it a p0420?

[wed3k]

o2 non fouler on the rear o2 sensor aka o2 spacer. this is how i get most p0420's to go away

[Losiracer2]

o2 non fouler on the rear o2 sensor aka o2 spacer. this is how i get most p0420's to go away

a spacer? like a washer?

[wed3k]

like modifying a 18mm spark plug non fouler to "space" the o2 away if you have the room underneath there. you usually run two spacers but sometimes the room will only allow one.

remember to use anti-sieze. how was the emissions?

http://www.civicforums.com/forums/22...on-w-pics.html

[Losiracer2]

like modifying a 18mm spark plug non fouler to "space" the o2 away if you have the room underneath there. you usually run two spacers but sometimes the room will only allow one.

remember to use anti-sieze. how was the emissions?

http://www.civicforums.com/forums/22...on-w-pics.html

and it won't affect how the engine runs, fuel economy, etc?

[s2cmpugh]

and it won't affect how the engine runs, fuel economy, etc?

It shouldn't. That last A/F sensor is simply used to check for cat. effeciency and does not effect the drivability of the car. The first A/F sensor has the primary job of determining air and fuel ratios.

This trick might work to make the CEL stay off, but all the emissions station has to do is stuck a probe up the exhaust and they can tell if something is wrong. Keep that in mind.

[Losiracer2]

It shouldn't. That last A/F sensor is simply used to check for cat. effeciency and does not effect the drivability of the car. The first A/F sensor has the primary job of determining air and fuel ratios.

This trick might work to make the CEL stay off, but all the emissions station has to do is stuck a probe up the exhaust and they can tell if something is wrong. Keep that in mind.

oh yeah AZ is really lenient, all they do is check for CELs and to see if the readiness sensors are ready and reading as they should. They'd even pass the car if only 1 of the readiness sensors is reading properly. In this case, they check the Catalyst and the EGR