p0420 - what to do at this point?

[Okie81]

Hi all, I was hoping to get some advice and maybe learn a little something in doing so.

I've been struggling with a p0420 code for the past 6 months now. There are many threads here that have been very helpful but now I am at a stalemate.

Here's what I've changed to date (in order):

• New left upstream O2 sensor (Denso)
• New left cat manifold
• New left downstream O2 sensor (Denso)

Correct me if I'm wrong but that leaves an exhaust leak as the only potential issue? I plan to check that out this week.

In the meantime, I pulled some live data with my BlueDriver app and it's apparent that the two downstream O2 sensors are not acting the same:



I have no clue what an exhaust leak would look like on the live data. Any thoughts would be appreciated.

 

[Bossman]

Toyota Parts | P0420 Diagnostic Code - Trouble Code Diagnosis Guide

Toyota 4Runner P0420: Catalyst System Efficiency - Below Threshold - Bank 1 | Drivetrain Resource

the dreaded "P0420". Mechanic's answer needed

Check Engine Light Code P0420

Code P0420, Cat or O2 sensor?

 

[duffdog]

This will fix it permanently:

Say Hello to my Lil Friend

 

[Okie81]

This will fix it permanently:

Say Hello to my Lil Friend

That's smart, and it may come down to that. Expect a PM from me once I'm ready to pull my hair out.

 

[2003-4x4runner]

Hi all, I was hoping to get some advice and maybe learn a little something in doing so.

I've been struggling with a p0420 code for the past 6 months now. There are many threads here that have been very helpful but now I am at a stalemate.

Here's what I've changed to date (in order):

• New left upstream O2 sensor (Denso)
• New left cat manifold
• New left downstream O2 sensor (Denso)

Correct me if I'm wrong but that leaves an exhaust leak as the only potential issue? I plan to check that out this week.

In the meantime, I pulled some live data with my BlueDriver app and it's apparent that the two downstream O2 sensors are not acting the same:



I have no clue what an exhaust leak would look like on the live data. Any thoughts would be appreciated.

I had the same issue and I just replaced both 02 sensors (upstream and downstream) and it fixed the issue.

I noticed you said LEFT . As I recall, the PO420 code is for the RIGHT side (passenger), Bank 1 on the V6 4.0. Could you have replaced the parts on the wrong side?

 

[Okie81]

I had the same issue and I just replaced both 02 sensors (upstream and downstream) and it fixed the issue.

I noticed you said LEFT . As I recall, the PO420 code is for the RIGHT side (passenger), Bank 1 on the V6 4.0. Could you have replaced the parts on the wrong side?

So p0420 is for the passenger side? Are you sure about that??

 

[lightfreak]

Bank 1 is wherever Cylinder 1 is, which is passenger side on the 4.0 V6

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)

Get a new Denso downstream sensor on the passenger side and you should be good to go. You already have driver side downstream sensor replaced so you don't have to worry about that side later on. They're not interchangeable since they have different length harness.

 

[2003-4x4runner]

So p0420 is for the passenger side? Are you sure about that??

I’m pretty sure. It was like 2 years ago when I replaced the 02 sensors. Shortly after, I got PO430 and ended up buying a new CAT on Bank 2 (driver side)

Also, that Blue Driver app is a bit odd? The screen shot says Left side, it should say bank 1 or bank 2. I read the reviews and it’s not that great. You may want to buy another App.

 

[Okie81]

I’m pretty sure. It was like 2 years ago when I replaced the 02 sensors. Shortly after, I got PO430 and ended up buying a new CAT on Bank 2 (driver side)

Also, that Blue Driver app is a bit odd? The screen shot says Left side, it should say bank 1 or bank 2. I read the reviews and it’s not that great. You may want to buy another App.

Thanks for the info.

I added the text to the screenshot, for clarification. But as you can see, I obviously had them mixed up. As for the BlueDriver app, I really like it so far.

 

[earthrealm]

Thanks for the info.

I added the text to the screenshot, for clarification. But as you can see, I obviously had them mixed up. As for the BlueDriver app, I really like it so far.

DOES IT SHOW abs/wheel speed sensors?, what of airbag?, am wondering if the app would work with any bluetooth driver, or if it must be a blue driver bluetooth

 

[Okie81]

DOES IT SHOW abs/wheel speed sensors?, what of airbag?, am wondering if the app would work with any bluetooth driver, or if it must be a blue driver bluetooth

No and no. I would guess that the app is proprietary to the dongle.

 

[Okie81]

... They're not interchangeable since they have different length harness.

Driver’s side downstream (the longer one) should work on both sides right? It’s just the passenger side with the shorter harness that will only fit in that respective side.

Let’s hope so because I did exactly that: took the one I replaced on the driver’s side and put it on the passenger side. We’ll see what happens

 

[lightfreak]

Driver’s side downstream (the longer one) should work on both sides right? It’s just the passenger side with the shorter harness that will only fit in that respective side.

Let’s hope so because I did exactly that: took the one I replaced on the driver’s side and put it on the passenger side. We’ll see what happens

Yes give us an update after a while. Just remember the longer the wires the greater the electrical resistance, Toyota likely took this into account when designing them.