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Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14505
Experience:  Toyota Master Diagnostic
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I have a 2003 Toyota Sienna, with code PO420 bank 1- mil, and

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I have a 2003 Toyota Sienna, with code PO420 bank 1- mil, and flashing ES, bank 2 is pending- with ES flashing. Pack rats chewed wires, but the van has 122,000 miles so we have replaced most everything that goes with the PO420 code. After we changed o2 sensors the ES started flashing. Thank you in advance for your help.

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What do you mean by ES is flashing? Did you get the wires all repaired correctly? are there any other codes besides the 420? Did you ever have any codes for the sensors that you replaced?



Customer: replied 7 years ago.
ES on the code scanner I have stands for Evaporative system monitor. It appears that we have replaced all the chewed wires, they were on the plugs.

As far as codes though you are only getting P0420? When you monitor the voltage of the rear or post converter sensor what is the voltage doing? Does it oscillate from .1 to .9 volts fairly frequently?



Customer: replied 7 years ago.
We have not done that.

The only way the 420 code can set is if the converter has deteriorated and the rear O2 sensor will show this because it will be fluctuating rapidly ie .1 to .9 volts 5 or 6 times a minute similar to an older upstream O2 sensor. If it is then the converter is no good. The converters are notorious to go bad on this van. If you do not need to have an emissions test done I would not worry about the code. The converters are very expensive and the aftermarket ons do not last.



Customer: replied 7 years ago.
I live in an area that requires testing. The confusion with this vehicle is that there is also a service bulletin out for the ecm. So that with the timing of the pack rats (no codes before they started chewing). This is turning into a very expensive fix. Also, when the lights come on for the engine because of this code, the braking system does not work properly. So if there is no fluctuating, what would be the next step?

Do you have the engine computer number or have you compared it to the listing in the bulletin?

Most of these were done under warranty along time ago. If you have the VIN I might be able to check it.

What wires exactly were chewed?

Spark plug wires or electrical?

What sensors did you replace?

Do you have VSC and TRAC and are these lights coming on you said?


Still need to know what the rear O2 voltage is doing. The logic in the ECU is not going to affect the voltae out put of the O2.



Edited by Skyvisions on 9/17/2010 at 6:13 PM EST
Customer: replied 7 years ago.
The VIN is 4T3ZF13C73U545503.

The wire to one of the rear fuel injectors was chewed, the injector was replaced.

All 3 O2 sensors were replaced.

All 6 coils/spark plugs were replaced.

And yes, the VSC and TRAC lights do come on when the engine light comes on.

I will not be able to check the O2 voltage until Monday.

Thank you!

I will check the vehicle identification number on Monday. If you can get me the number that is on the side of the computer that would be helpful also. It should start with 89661 then five other numbers. Let me know on Monday what you find on the O2 voltage swings and I will get back to you. Ideally if you have an oscilloscope that is the best way to monitor the voltage if you see a sine wave pattern developing rather quickly this means the converter is deteriorated and is not doing its job. Have a great weekend.



Customer: replied 7 years ago.
We were unable to check it with an oscilloscope, but purchased an AutoScanner Live data reader by Actron. I am hoping you are familiar with this scanner. Thank you!

I am not familiar with that specific scanner at all life data code readers and scanners are about the same. You need to monitor the O2 sensor that is after the catalytic converter this should be listed as sensor two. This voltage should not be swinging from .1 to .9 V rapidly. It should have steady rises and steady decreases. If the voltage swings go from .1 to .9 V several times within a minute this means the deteriorated catalytic converter is not doing its job. They did change the logic in the engine control computer to help correct for this but if the converter is bad the computer cannot override it. Were you able to get the engine computer number? Is this the original converter? If this is the original converter you're probably going to have to replace it. If you purchase an aftermarket converter keep in mind that it will not last as long as the original factory installed equipment. It is cheaper for reason.



Edited by Skyvisions on 9/22/2010 at 2:14 PM EST

Normally aftermarket converters are only good for one or two years. If you're not planning on keeping the van longer than that it shouldn't be a problem. If you are see if you can find a converter that offers a lifetime or five year warranty.



Edited by Skyvisions on 9/22/2010 at 2:18 PM EST
Customer: replied 7 years ago.
OK....With the live scanner hooked up, during idle this is what it is reading:

O2 S12- .675 to .205
O2 S11- 3.274 to 3.283
O2 S21- 3.269 to 3.293

While driving:

O2 S12- .150 to .685
O2 S11- 3.171 to 3.303
O2 S21- 3.171 to 3.313

They are all fluctuating at the same pace, more than 10 times per minute.

This is the original converter. Thank you
Customer: replied 7 years ago.
ECM #TN175200-9301 12v 1MZ-EF

Toyota sticker on ECM- 89661-08080

Based on the information above if O2 S12 which is the rear O2 sensor or post catalytic converter sensor is fluctuating from .150 to .685 more than 10 times a minute the catalytic converter is bad. Your other sensors that are averaging between 3.1 and 3.3 V are the AFR sensors ideally to run 14.7 to 1 air fuel ratio these voltages should be right around 3.30. They will fluctuate up and down by .1 or .2 V on acceleration and deceleration this is normal but when the engine is idling they need to be right about 3.3 V. your computer is also not up to date as per the latest technical service bulletin. The technical service bulletin is EG047-05 according to that service bulletin the new updated number should be 89661-08081. Both the catalytic converter and the engine control module are only warranted for eight years or 80,000 miles. If your goal is to keep his vehicle long-term aftermarket converters are usually only good for a couple of years they do not last because they are cheap for a reason.



Customer: replied 7 years ago.
So we need to replace the converter, but what about the ECM?

You need to start by replacing the catalytic converter. The problem is what comes first the chicken or the egg? These converters were notorious to go bad but no one has really determined whether or not it is the fuel calculations in the computer that prematurely ruined the converter or did Toyota change the logic in the computer just to keep the p0420 code from setting prematurely? That information will never be known. The computer front is going to be very expensive probably 800 or thousand dollars. There is a chance you might find the updated number in a salvage yard but that would be a long shot.



Skyvisions and 2 other Toyota Specialists are ready to help you
Customer: replied 7 years ago.
I appreciate your time and patience, we will replace the converter. Thank you!

You are welcome. If you need any further assistance or any help in the future just ask for me Skyvisions, in the question and I will get back to you.