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Help with CEL P0420 on 02 Prerunner

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Old 11-08-2011, 07:45 AM   #1
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Help with CEL P0420 on 02 Prerunner

I'm really at a loss on what to do about this code. I'm hoping somebody on TW can help me out. I've got a 02 PreRunner with about 160K miles. As far as I know, the catalytic convertor, O2 Sensor and A/F Sensor have not been changed.

I recently got the P0420 code. I read up on the forums and did some of the inspection checks listed in the FSM - DTC P0420. I checked for exhaust leaks, but didn't notice any. I used my voltmeter and both sensors seem to be in tolerance. I removed the A/F sensor and cleaned it in SeaFoam then sucked about a 1/4 cup of SeaFoam into my PCV Valve to clean out any engine carbon build-up. I got Advance Auto Parts to clear the code and thought everything was cool.

Then a couple of weeks later, the code hit again on my way to work. I'm at a loss what to do. Here's my thoughts... 1. Clean the O2 sensor (I haven't done this yet since I didn't have a deep 12mm socket to reach over the heat shield.) 2. Pickup a OBDII Checker and do my own "OBD II ACTIVE TEST". (This may give me an excuse to buy a BlueTooth OBDII.) 3. Replace catalytic converter. (Not too excited about this one. RockAuto lists a WALKER Cat# 53432 for $170, but I'm thinking installation will probably be costly.)

Has anybody successfully solved this problem?
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Old 11-08-2011, 07:57 AM   #2
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I also found these posts over at http://www.p0420.com/. Not sure if they apply in this case though...

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On thing that not a lot a people think of checking is the Ethanol rating in the gasoline they use!! Toyota tacoma are set to use Gas with less then 10% ethanol... So what i did is I empty my tank and filled it back with ethanol Free Gasoline, unplug the battery to erase the codes and Guess what, no more light...
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To minimize this risk, it's a good idea to check the operation of the O2 sensors with a scan tool or scanner software. You should see normal switching activity in both sensors shortly after the engine is started, with the O2 sensor voltage switching back and forth between rich (over 0.8 volts) and lean (less than 0.3 volts). A flat line O2 sensor reading or one that shows little switching activity is a bad sign. The downstream O2 sensor should slow down and go flat when the converter lights off (if the catalyst is working). If it keeps on switching like the upstream sensor, it tells you the catalyst is probably bad and the converter needs to be replaced.
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Old 11-09-2011, 11:12 AM   #4
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Is there anyway to check the cat first?

I'm going to try to check the 2nd flange this weekend too as that worked for another TWer.
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Old 11-30-2011, 05:53 AM   #5
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Did you eventually fix this problem? What was the final resolution?
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Old 11-30-2011, 11:29 AM   #6
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I got the CEL reset and it remained off until my last fill-up. Since then, I've had some higher priorities and haven't gotten around to it yet.
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Old 12-07-2011, 08:41 PM   #7
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I'm having this same issue. If you figure it out let us know. I'm also thinking of picking up an obd II aswell just to look a little deeper. I was told by a mechanic that it's probably the cat itself if no exhaust leak, clean MAF sensor, good 02 sensors. which sucks. I don't want to pay for one of those stupid things, but am at a loss. I'm not getting any noticable changes in power at this point but he said it will probably start if I don't fix it at some point soon.
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Old 12-08-2011, 06:04 AM   #8
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I've noticed a decrease in power and gas mileage lately. Got to work on this as soon as I wrap up school. I've cleaned my MAF sensor. (It needed it.) Next I'lll need a deep 12mm socket to clean the O2 sensor without having to cut the heat sheild.
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Old 01-09-2012, 09:59 AM   #9
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Here's the latest update on my CEL issue. First, I cleaned my O2 Sensor with SeaFoam. Then, I followed the advice of el contrador to check for leaks around the exhaust flanges. I ran some SeaFoam into my PCV value and let it sit over night. (The SeaFoam burns white smoke after letting it sit for a while.) In the morning I got a friend to block my exhaust with a board while I looked for the white smoke leaks from the flanges. No noticable leaks.

After all that, I reset P0420 codes. It's been one week so far with no CEL. So maybe the O2 sensor was dirty? I also stopped getting gas at Kroger to see if the issue may be related to the brand of gas I use. (I've consistently been using Kroger Mid-Grade 89 Octane.) I'll check back soon with status.
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Old 01-09-2012, 10:08 AM   #10
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Old 01-09-2012, 08:15 PM   #11
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I had this code once po420 changed both 02 sensors and the cat , trouble went away for about a year and i got it again about a month ago after returning from hunting cleaned MAF and put HEAT in my gas and cleared the code and havn't had it since ?. heard moister in the gas can cause this.AKA Alcohol.
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Old 01-10-2012, 08:21 AM   #12
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Quote:
Originally Posted by agapedisciple View Post
Here's the latest update on my CEL issue. First, I cleaned my O2 Sensor with SeaFoam. Then, I followed the advice of el contrador to check for leaks around the exhaust flanges. I ran some SeaFoam into my PCV value and let it sit over night. (The SeaFoam burns white smoke after letting it sit for a while.) In the morning I got a friend to block my exhaust with a board while I looked for the white smoke leaks from the flanges. No noticable leaks.

After all that, I reset P0420 codes. It's been one week so far with no CEL. So maybe the O2 sensor was dirty? I also stopped getting gas at Kroger to see if the issue may be related to the brand of gas I use. (I've consistently been using Kroger Mid-Grade 89 Octane.) I'll check back soon with status.
Yea let us know. I think I'm going to get the sim from urd and start with that. I did the Seafoam thing without any noticable changes. I think my mpg's are dropping as of lattely. I've also been looking at cats, and cause my trucks Cali. emmissioned I have two of them. I've read on here that afftermarket cats don't last at all, but it's hard to look past how much cheaper they are.
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Old 01-30-2012, 07:29 AM   #13
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Been 4 weeks and still no CEL. Gas mileage didn't look good on my last fillup so I'm still at a loss as to what the issue really is... wonder if changing the O2 sensor is the right solution.
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Old 01-30-2012, 07:32 AM   #14
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Had the same code on my 2nd gen. Turned out to be cracked manifold!
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Old 02-15-2013, 01:47 PM   #15
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Finally changed the O2 sensor about 7 months ago. Haven't had the CEL come back since.
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Old 02-18-2013, 08:11 AM   #16
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I changed my downstream sensor and still had a problem. Ended up having to change my catalytic converter. No problems since then and it's been over six months.
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Old 12-20-2013, 09:39 AM   #17
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you can check the catalytic converter by using a scan tool. monitor the no.2 O2 sensor voltage while the engine is running. the voltage should change very little even when you rev the engine. if the voltage is fluctuating a lot than the catalytic converter is bad. always go with toyota brand.
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