P0420 Code and Serviced the Parking Brake This Weekend

[Polak]

Serviced the rear brakes including the parking brake this weekend and it all looked exactly like THIS so salt belters take heed.

Also, Friday on the way to work the CEL came on. Stopped by Autozone and they pulled P0420 and reset it.

After searching it looks like the 420 code could be multiple issues. My question to anyone with any experience w/ this code is - What worked for you?

My plan is to search for leaks pre-cat and replace the O2 sensors as I'm sure these are the originals.

Thanks for any help,
Polak

 

[tonyr0d]

I have a 95 that was giving me a p0420 code so I replaced both o2 sensors with oem ones and haven't seen it return in 4 months. Hope this helps.

 

[concretejungle]

mine threw this code after one of my first couple of wheeling trips with the truck. First i replaced the O2 sensors. Reset the code; stayed off for a few hours then was back. Note, i probably needed to replace the sensors anyways since they had about 150,000 miles on them. Next i remembered that i did hit my exhaust. So i climbed under the truck while it was running and you could feel an exhaust leak at the flange between the two cats. I ordered a new gasket from Cdan, replaced the gasket, reset my lights and it fixed it. It's been over 50,000 miles since.

 

[AZ2ME]

I had the 0420 code coming up and found several exhaust leaks: at the intersection of the y-pipe, and at all of the gaskets. I think the system is original (235k miles), so not a biggie.

New O2 sensor and gaskets and the requisite handful of nuts and bolts and so far so good.

Only about 300 miles since I finished, so don't know yet if that was the source of the problem.

 

[NoMoreFires!]

Meow time for some kitty cats!

RUn tests before hand, but prolly needing at least 1 catylitic converter

hope this helps

DTC P0420 Catalyst System Efficiency Below Threshold

CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of the oxygen sensor located after the catalyst to determine whether or not catalyst performance has deteriorated.
Air-fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeatedly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the catalyst.
But when both waveforms change at a similar rate, it indicates that catalyst performance has deteriorated.

DETECTING CONDITION

SYSTEM CHECK DRIVING PATTERN

(1)Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.(2)Start and warm up the engine with all accessories switched OFF.(3)Run the vehicle at 50 ~ 65 km/h (31 ~ 40 mph) for 5 ~ 10 mins.
HINT: If a malfunction exists, the MIL will light up during step (3).

Step 1

Step 2

 

[concretejungle]

Thanks for the helpful diagrams Ryan.

If it were me, i would start at the cheapest possibilities first. IE: exhaust gaskets, then O2 sensors. Then cats.

 

[NoMoreFires!]

you can do that if you want, but if there isnt anything wrong except the cats then youve just burned up dollars that coulda gone toward replacing them in the first place, in my business it is our job to properly diagnose the problem the first time so that the customer has to spend as little money as possible so thats why I posted the flow chart. If you have an exhaust leak btw, you are more likely to kick a lean code or even an o2 code (yes there are codes for specifically the o2 sensors) a p0420 code is very specific, and you can use more decent handheld scanners to measure the outputs from both the #1 and #2 o2 sensors to determine if the the problem is actually the cats.

 

[CJF]

My plan is to search for leaks pre-cat and replace the O2 sensors as I'm sure these are the originals.

That's exactly what I'd do.

Curtis

 

[concretejungle]

you can do that if you want, but if there isnt anything wrong except the cats then youve just burned up dollars that coulda gone toward replacing them in the first place, in my business it is our job to properly diagnose the problem the first time so that the customer has to spend as little money as possible so thats why I posted the flow chart. If you have an exhaust leak btw, you are more likely to kick a lean code or even an o2 code (yes there are codes for specifically the o2 sensors) a p0420 code is very specific, and you can use more decent handheld scanners to measure the outputs from both the #1 and #2 o2 sensors to determine if the the problem is actually the cats.

Understood. But again, that is exactly what the dealer told me and tried to sell me cats. They said the same thing that it was their job to diagnos the problem the first time, ect.... Ended up just being a $5 gasket between the two cats. I decided to replace the O2 sensors while i was there since they had almost 200,000 miles on them.

 

[NoMoreFires!]

Just for reference I wonder how much the dealer charges for cats? I bet we do them for less than half (of course we still make a substantial profit) we do mostly catco and magnaflow cats just weld in style with all the proper attachments

 

[Polak]

Just for reference I wonder how much the dealer charges for cats? I bet we do them for less than half (of course we still make a substantial profit) we do mostly catco and magnaflow cats just weld in style with all the proper attachments

I seem to remember a post where someone was quoted $1200+ at the dealer for new cats.

 

[MTBGUY]

I went through this about two years ago. The cruiser would get the 420 code, and I would reset about once every two weeks. I replaced both o2 sensors on my own then and had an exhaust shop check for leaks (they charged nothing- and have a special "sniffer" tool).

I would still get the 420 code occasionally (once a month) and then it became more frequent again. I finally had an aftermarket multistage high flow cat welded in to take place of the two single stage cats in my 97 model.

I've never had the code again- its been about 18 months now.

I would start with checking for leaks first (esp. around the gasket flange at cat.), then replace sensors with Toyota OEM, then lastly try the Cat replacement.

Some states allow the single cat replacement and some don't - so make sure your state doesn't actually look under the car to count them if you go with a newer single high efficiency model.

Cost of welded in aftermarket was about $250 for me.

 

[NoMoreFires!]

hmm im pretty sure our price on both cats hi-flow installed would be like 450, but just taking out the 2 putting in straight pipe then after the y putting in 1 single hi-flow would be roughly 270

we use magnaflow or catco......ive sole tons of cats on 420 codes and as long as their arent other problems it always fixes it and its never came back on again....the only time ive ever seen a 420 come back on after a cat install was on an odyssey van, because the shop that did it (not us) put on a cat 2 sizes too small for the van and, i ended up selling a new honda cat (i worked at the honda dealer at the time) if it were now id just put on a catco that was the proper size and call it a day!

 

[C6H12O6]

One more data point for the $5 gasket fix. I banged the exhaust wheeling, bent the under-the-frame tube behind the cats, and broke the gasket between the cats. 10 minutes and 5 bucks fixed it. Three years and no return.

Start cheap. Check for leaks.

 

[MTBGUY]

Two years now and.... ITS BACK................O2 sensors are Toyota OEM replacements, Cat was replaced, no cracks in welds anywhere in exhaust. I wonder if the shop put in a Cat that was undersized? I took it recently on a 600 mile trip w/no problems. The next day it gave me the 420 code at 35 mph on way to grocery store.

 

[C6H12O6]

Reset it and see if it comes back before you stress too much. I just had a broken hanger fixed and a crack in the muffler welded up and it was fine for a couple days of highway driving and wheeling. On the way home, driving 40 mph, it came back. I drove to Autozone, had it scanned (PO420) and reset the computer by pulling the EFI fuse. No problems since.