Do I need to replace the Catalytic Converter in my 2005 Toyota Highlander V6 2WD?


Asked by sarabeth143 Dec 13, 2013 at 04:35 PM about the 2005 Toyota Highlander

Question type: Maintenance & Repair

2005 Toyota Highlander V6
217,000 miles
Maintained at the dealership until Dec. 2011
One very loving owner. Bought her brand new with 17 miles total including my test drive.
Time of purchase through the summer of 2009: All routine maintenance was done at the
same dealership.

2009-2011: Moved to Austin and took it to one consistent dealership.

Aug. 2011: Replaced all the O2 sensors
Went into the dealership for an oil change and tire rotation on the way home all the lights
came on. Called them right then. Went back the next morning. No clue what the code was
but replaced the O2 sensors. Toyota did not verbally tell me and the paper work is long
gone due to a misplaced box after a move.

Dec. 2011: All three lights came on again. Code PO420
This time Toyota told me I needed to replace the Catalytic Converter. I refused and
traded cars with ex. He drove my car for two days and the lights went off. It passed
inspection. I traded back. I love my Highlander and his Camery is kind of a snooze fest.

Feb. 2012: The lights came on again. They had been on and off since then. Not sure if
this will help my case or make me sound nuts but...
*For months the lights would turn off if my car was really dirty and I drove through a car
*Then it completely switched and they would come on if it rained or I took it to the lake.  
I know, I know, I said it was going to sound nuts...

Sept 2013: They have been on full time going forward.

November 2013: Lots of various codes (all related to the catalytic system). Replaced the
Spark Plugs and still had lights. Replaced the Mass Flow sensors and the lights went out.
I drove 100 miles and the lights came back on. Guessing the computer just caught up...   

I took it in today: The codes were PO430 and PO429.

My gas milage has recently gone done dramatically (16 mpg) but I am not feeling any
performance issues. I am pretty sure you are going to tell me to replace the Catalytic
Converter(s) but I was curious if it could be anything else? I was also curious which side
of the engine bank one is on (since the PO420 reading had to do with bank one)?

6 Answers


Sorry for the typos.

3 out of 3 people think this is helpful.
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....well the catalytic converter simply changes the poisionous CO gas into C02 and nitrogen and water can pretty much sniff the exhaust to tell if it has any CO in it...modern keyboards are not suited to typing....more like pickin' a dime off the sidewalk with mittens on...that's why I INSIST on an IBM M-30 clicky can still get them on Ebay....back to the problem....frequently "heated" 02 sensors aren't getting solid 12.5 volts and sufficient amperage for them to do the job of analyzing how much oxygen is in that before and after the cat as a kind of safeguard....the mileage does not matter as much as the SOLID connection to ground from the Black battery cable....Follow this black 1/0 Cable down to where it attaches to the fender/frame....disassemble...wirebrush the lug free of corrosion till shiny...then wirebrush the chassis to make a solid electrical connection there as this one will see 300 cold-cranking amps and through a blue spark from repeated starts forms a layer of "semi-conductor" which will not allow the full voltages and hardly none amps through sure the battery is newer than five as they will degrade 10 percent per year...right off the far as "normalizing" the combustion....take it on a nice long higher demand drive so the catalytic converter will blast thru/clean off the unburned deposits....and the o2 sensors too~ look for an M30 for typing pleasure~

2 out of 2 people think this is helpful.
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DEFINATELY sounds like the MAIN ground connection is not doin' it's job....because the ECU when subject to varying voltages and available amps will throw up the trouble codes...after refreshing the ground effect "fixing" the ECU should read the codes with a handheld scanner, then "RESET the Codes" ...which this scanner will offer to remove the codes that have been stored...because they will be WRONG with 02 sensors who's heating element is comin' up to temperature now....and monitoring of the performance by switching the EGR off and on as needed will work finally...all devices what are supposed to work WILL work now...if you do as I say~

2 out of 2 people think this is helpful.

Thank you soooooo much! I will try this over the weekend and report back.

2 out of 2 people think this is helpful.
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2 out of 2 people think this is helpful.

Take the 02 sensors out start the car and see How clogged up it is of ot is clogged up The air will be coming out of 02 sensor hole like mad If the air is not coming out bad sensor can be replaced

1 out of 1 people think this is helpful.

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