P0420 and P0300 - 2000 Taco V6 - Need to Pass Smog

Hello


After taking my 2000 V6 Tacoma in for a diagostics test figure out why I’ve got a check engine light on, according to the shop the codes presented are P0420 and P0300 (general misfire).

According to the shop, I’ll need both cats replaced to address the P0420, and a tune up to the address the P0300. Both issues, both codes will need to be resolved to pass smog.


The tune up includes:

Wires and Plugs. I replaced the spark plugs 2 years and 22,000 miles ago, and I can’t remember if I used denso or NGK plugs, but I think I got platinum tip – but again can’t remember and my log is in my truck with is at the shop. Surprised they would be shot by now, but if the fuel is running rich? Maybe I don't know.


Does this info sound right? Cost of everything is about $1,400 – I’m in so cal.


I"ve heard some people in this situation suggest that a fuel pump may need replacing, and or the MAF needs cleaning. I don't want to do these repairs in vain, and also if the fix is cheaper and elsewhere of course want to address the actual issue.

 

Sounds like you need to get a copy of the FSM and do some diagnostic work/troubleshooting. That DTC, P0420, can be caused by things other than what the shop told you. I doubt they truly diagnosed it and just simply looked up that P0420, WHICH STATES: CATALYST EFFICIENCY BELOW THRESHOLD.
So I see two options for you, get the FSM steps and tests for troubleshooting P0420 DTC,
or pay a shop to shotgun parts at it. Or get them to guarantee the cats are bad and to guarantee the P0420 will be taken care of by what they perform.

 

Thanks - good advice.

Factory service manual
it's in my truck

I'll see if I can find one online

 

Oh you have the repair manual already? Yeah man troubleshoot that thing yourself. There are some working links for digital versions of the FSM too, just seem a little harder to use.

And it may very well be the cats not working as well as they should, but there are a few other things we see here on the forum that cause the ECU to detect that same condition of the cats not working as well as they should.
Exhaust leaks and intake/vac leaks can cause this DTC to show up. Any 'unmetered' air, whether escaping the exhaust before the O2 sensor or unmetered air sucked into the intake system after the MAF has measured it can cause this issue.
I don't think it's very likely your 2 year old 20k mile plugs are fouled or bad. Possible, just not likely at 2 years old.
There are some specific shops that deal with only or mostly all Toyota as well and they'll be much more familiar with the typical issues our first gen tacos run into

 

Also, definitely clean your MAF sensor with the appropriate cleaner, like you mentioned in your first post. I didn't acknowledge that in my post but you're right on wanting to do that before the big money stuff

 

I would do the tune up first and see if it addresses your misfire and subsequently the P0420, but its likely the misfire did the damage to the cats if it wasn't fixed in a timely manner. So new cats probably needed as well. But definitely fix the misfire first or you'll risk damaging the new cats too

did you do the wires too when you replaced the plugs last time? Or are the wires still original?

 

I have been seeing the 0420 occasionally, never paired with 0300, but can offer advice from what I did that helped get rid of the 0420 code I had paired with 0171. I have cleaned the MAF sensor with a q tip and rubbing alcohol like here http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.htm#maf which I believe got rid of the 0171 because I only got that once and it hasn't come back. One that has is the 0420, which I can keep at bay by running mid-grade fuel. Not 85, 87 or higher. Just a week or two back it popped up, (I had been on regular for a few months) so I ran to O-Reillys, Checked it, and once I was almost out of gas I filled with Plus, 87 or whatever. After about 50 miles it turned off. Easy! As long as you don't think about the fact there may be a bigger issue...

 

Your P0420 code was directly caused by the P0300 code. I've seen this one too many times to be telling you this. They are recommending the secondary cat because it is ready to go out as well and their data indicates as such.

If they are quoting you $1400 to do both cats (factory) alongside the tune up I would say that is quite a bitchin' price. Go for it and make sure the P0300 code stays away after. Make sure you have their guarantee that whatever they are recommending will fix the issue and if it does not they will continue diagnosis for the misfire. This puts you in the clear in having to invest additional cash after repairs are done and puts them on the hook for making right in their repairs.

After that is done, drive the vehicle some 200 miles and have them recheck your emission component monitors, make sure they have all passed. Once they have, you're good to go, take it to smog and enjoy your truck.

 

2 cats should be $300 ($150 each) if you buy aftermarket (get the CARB compliant, obviously, since you have the Cali model) + $80 to weld. I've had a magnaflow cat on mine since a P0420 code 4 or 5 years ago now.

No idea why you have a misfire, put your plugs are probably fine (check them, and double check you gapped properly while you have them). Wires are like $50 and a super easy install yourself.

For $1400 you could have all that shit done and have enough leftover for some sweet coilovers.

 

Agreed, I had the p0420 code a few years back and got both cats replaced with CARB Magnaflows for $600 at an exhaust shop. Codes been gone ever since. A tune up even if done by a shop shouldn't be more than a few hundred or less. $1400 seems steep for aftermarket cats and a tune up.

 

Forgot to mention that the intake manifold leaks oil over the top and on to the engine, which is common with this engine - + I've got 300k miles on the orignal engine - never rebuilt. I hope I don't have to get that fixed to pass smog. BUt the intake manifold is outside of the actual compression or metered air equation correct?

Good to know, however I've got a $135 diagnostic fee with this shop (credited towards repairs)

 

Uh...technically correct, but not out of the doghouse. I'm assuming you mean the plenum leaks oil? If you have a serious leak there, you'll be drawing more air than the MAF has accounted for, giving you lean condition and the ECU will compensate by adding more fuel.

I've only ever had oil mist from there, never a full leak...might need a pic.

 

I just replaced the plugs 20k ago. I believe the wires are original, as I don't have record of them, but it's possible I forgot to log that and I may have replaced them many years ago. I'm pretty confident they haven't been replaced for at least 100k miles

So you are saying do the tune up, drive it, try to smog it again and if it fails, do the cats, rinse, repeat?

 

Understood. Hope these guys get you squared away fairly and promptly.

 

Here's the quote, breakdown:
..... Labor / Parts / tax / total


Wires 0 / 78.99 / 6.32 / 85.31
Plugs 94.50 / 150.00 / 12.00 / 256.50
Cat 1 135.00 / 474.00 / 37.92 / 646.92
Cat 2 108.00 / 275.00 / 22.00 / 405.00

Total 337.50 / 977.99 / 78.24 / 1,393.73

Sorry it's not aligned

 

Well I would drive it after the tune up but I wouldn't smog it unless you know for sure the P0420 is gone, if you have a code reader you can hook it up and see if the code is still in the system. A lot of times people think the P0420 is gone because it doesn't show up on the dash or code reader, but that's because the truck's emission cycle is still incomplete. And you can't get smogged with an incomplete emissions cycle, they'll turn you down.

You can monitor the emissions cycle via a code reader. If there's no code and the cycle is complete, you're good to go get smogged.

Kind of a pain but the cycle doesn't take long to complete. This is why it's not recommended to get smogged if you just replaced your battery or had it unhooked recently, cause it causes the cycle to start over. Usually takes a bit of driving to get the emissions cycle to complete itself.

In all likelihood you probably do need new cats, I'm just saying it's better to fix the misfire first so you don't damage the new cats in the process

 

That's way too much for aftermarket cats (and way too cheap for OEM cats). OEM cats are crazy expensive but a good set of CA compliant aftermarket Magnaflows are only a couple hundred each, plus maybe another hundred or two to weld them on. Depends on where you live I guess but they are way overdoing it on the cats IMO

 

Not sure what to tell you. They're overcharging on everything.
Looks like their basis is $150/hour for labor and must be getting their parts diamond encrusted.

 

I would have an exhaust shop give you a quote on new cats, they'll usually have the better deal than a general repair shop. Get the tune up done elsewhere (exhaust shop may even do that too)

 

I knew off the bat the spark plugs were high. So I was planning to check the cats too. I can get my own parts. THey may charge me a "fee" for that, but it will probably be cheaper.