Need help - check engine light code p0420

Can you elaborte on this? I think I may have the same issue judging from the sounds the truck is making and the P0420 code it just threw.

 

This is a pretty common code for toyotas. Basically if you are running a lot of low speed driving like around town, the system gets bogged down. It's not a big deal, you can still drive the truck for a long time, just reset the cel. Look into replacing your O2 sensors soon. Get denso sensors only. You can get them from rock auto pretty cheep.

 

Thanks. I do a lot of city driving so hopefully I fall into this category.

 

Just happened on my truck

Same code

2001
193k miles
Automatic
4 cylinder

So it's definitely new Cat time ?

Best place to buy Cat ?

 

Replace O2 sensors first!! CAT's very seldom go out, it is the O2 sensors 99.9% of the time. The O2 sensors are a replacement item under normal service (interval of about 60,000 miles) DO NOT REPLACE THE CAT UNLESS YOU KNOW FOR CERTAIN IT IS BAD!!! In either case, go to Rockauto.com for all parts, they have the best prices. If you have any other questions feel free to PM me or you can email me at ki6pyr@gmail.com

 

Thank you Joey

I reset the code for now

I am on a 800 mile trip with the truck

After I reset it last night today drove it 300 miles
It has not come back yet

Once it comes back again , if it does, I will send you email about 02 sensors

 

1100 miles driven
Haven't come back yet

 

Regarding tests to determine if a cat converter is bad, I read that you can use a digital thermometer to measure the temp entering & leaving the cat. Supposedly, (for a 1 cat system) the temp leaving the cat should be around 100 degrees greater than the input temp. My 2001 Tacoma has 2 in line cats so, how should one perform the tests ? Read each cat individually ? or
read temp entering cat 1, then read temp leaving cat 2 ? My guess is the temp leaving each cat should be greater than the temp entering each.

Had a P0135 code, replaced upstream sensor, reset CEL. Now have a P0425 code. Shop says it's the cat. Trying to determine which cat ! Guess I should not worry & replace both.
At this point, I'm just playing around with it, the truck runs fine, gas milage is good etc etc. I am the 2nd owner, milage is just 79k, but owners man sez plugs should have already been
replaced etc. I am in a non emisson test state (Va.), so guess I could do away with 1 cat ? Ohh well, enough rambling ! Nice thread, I just joined.

 

If a cat is bad, 9 times out of 10 it it the front cat. Measure the temps of the two cats. The front cat should be significantly hotter then the rear cat. If they are very close to the same temp then replace the front cat. I recommend going to rockauto.com for a new cat. Eastern Catalytic is the brand I used when I replaced mine. If I had it to do over again though I would use a magnaflow. Make sure you follow proper procedure to "break in" the new cat. It's not hard to replace the bolt in one, should only take about 30 min. Any other questions feel free to email me. ki6pyr@gmail.com

 

So, I just ordered a magnaflow cat for my 2001 Tacoma. 2.4l, except, I only ordered the 49 state compliant one, which is not CARB compliant for the state of California. but I noticed that my truck is compliant for California emissions. I don't live in California, so that doesn't matter to me, but my questions is: If I don't put in a CARB compliant Cat, am I going to keep seeing the CEL? Wondering if I should return the Magnaflow when it gets here and order the 50 states CARB compliant one..

 

I can't say for sure that it will, but seeing as how the O2 sensors are also California sensitive, I would imagine that it would trip the CEL. I would return it and get the ca one. Better safe than sorry. Any further questions, drop me an email. I only check this every week or so. ki6pyr@gmail.com

 

I had this code as well and it turned out to be an imperceptible exhaust leak. The gasket between the parts failed but left no noise or visual indicator. The slightest intrusion of air WILL trigger O2 sensor ( picture a Venturi as it draws in air ) and signal computer that CAT has exceeded it's life when in reality it's still functioning. After gasket replacement all is still good. Even at high milage our CATs are usually still working. An engine that spews oil or anti freeze into exhaust stream will foul a CAT early and usually ours never do that. MAGNA FLO is your best option if yours is gone. Good Luck.

 

Bad news. No 50 state cats available from Magnaflow unless you get one of the weld on ones.. I don't weld nor do I want to deal with that hassle.. So I ordered a bosal brand cat 50 states. used a 20% off code and got a decent deal on it. http://www.jcwhitney.com/bosal-50-s...86.jcwx?skuId=7856318&filterid=d2193y2001g2j1

My cat is in terrible shape, falling apart and held together with tie wire, so, I'm pretty sure that's the problem.. I hope..

 

What a pain in the ass to install.. I had to grind off the rear bolts and then I had to have a 15" extension on my impact gun to get off the other ones.. took me 4 hours to do the whole install because the bolts were just melted together from all the heat down there.. anyways, got her done and cleared the codes.. still waiting on the catalytic monitor to complete it's cycle.. it's been a couple weeks.. usually takes a bit for that one to finish. Hopefully the P0420 code doesn't come back on.

 

Since the above was posted, I've been playing around with this situation and thought would give an update. Purchased a scanner (

$56 Bosch 1150 Trilingual Scan Tool with AutoID, Live Data, ABS and Graphing

Bosch 1150), tried higher octane gas, tried gas tank additives and during all of these things, the old 0420 code kept reappearing after being reset (many times). Then, I had my shop do lots of things (that should have been done b4 79k miles). They replaced the plugs and plug wires, timing belt, water pump, fuel filter, auto trans fluid & filter, and belts & hoses. Upon picking her up from the shop, I (of course) did a test run and not long into the run, the pesky CEL & 0420 code resurfaced. I reset the code and decided to order the front cat converter assembly, because I just knew the 0420 would keep returning !! WRONG, it's been 2 weeks now and no more codes ! FYI, today I made cat converter temperature readings starting at input/output of cat1 then cat2, The readings were made at normal idle with a warmed up engine. Readings were 300f, 440f, 300f, 350f.

I may be putting a Magnaflow Cat part number 51679 up for sale ! I will re post with the final outcome

 

That's some good news! Did your cat converter monitor perform it's full drive cycle and everything's green? I'm at 2 weeks with my new Cat and no CEL but my Cat converter monitor has not completed it's full drive cycle.. the drive cycle for that is ridiculous and sometimes takes a bit to complete.. just wondering if you checked if it was complete.

 

Hi Nate & thanks for the reply. I have not installed the new Cat yet, in fact it has not yet arrived. Since the shop work was completed (2 weeks ago) I've been codeless ! hope you stay codeless also.

 

Oh ok. I thought you had installed a new cat. So, the question still stands, Have all your monitors completed their drive cycles? Are they all reading as 'completed'? Namely that catalytic monitor. that's where the P0420 code comes from. But if it hasn't completed the drive cycle it will show as 'not complete' and won't pull a code or light up the CEL, if at all, until it's completed it's drive cycle. Just wondering, because it's been 2 weeks for me as well and I drive mine everyday but haven't gotten that monitor to complete its drive cycle.. it always takes the longest to complete that one.

 

Another 1000 miles added


So 2100 miles since I reset the CEL
Not back yet

Possible it was out if state hill billy bad gas ?

 

Hello Nate. Well, not sure I know how to answer but here goes. Prior to having the plugs, plug wires & timing belt replaced, I would get the 0420 code every few days. I would clear the code and in 2 days the code would be back again. I checked it so often, that I could see when a code was pending etc. Since clearing the code immediately after the shop work was completed, there have been no codes or pending codes. This Tacoma is not driven a lot, but its been driven enough that the CEL would have been back on if the shop work had not been done. I guess a new drive cycle starts every time a code is cleared ? If that's the case, the CEL should be back on by now, based on pre shop work performance. I will be looking out for the CEL, if it returns, I'll install the front cat (it's on the way)