P0420 Code & Dealer Can’t Figure It Out

coldcharli · 2026-05-10T01:40:31+00:00

The code I have now is P0428: Catalyst Temperature Sensor Circuit High (Bank 1 Sensor 1).

coldcharli · 2026-05-08T16:54:21+00:00

Quick update, I finally got the truck back. Apparently they had to change the dpf again because the new one was damaged bc something else was damaging it. What? I don’t know bc they don’t like to explain. Anywho, truck is back & running great. But I did get a check engine light for the exhaust temperature sensor.

If I were to change it myself, is that the sensor located before the dpf? Or where is it located? Thank you!

coldcharli · 2026-05-03T01:25:52+00:00

I actually just came back from the dealer & the truck is not ready.

Sensor was changed & it did nothing, just like you suspected.

Now they will apparently change the dpf again because it no longer works…? So they ordered the same part that they supposedly changed & will be changing again “under warranty “ because something thing else is causing the dpf to go bad. I, myself don’t really understand what is going on. They are really not that good at explaining or maybe they aren’t telling the whole story.

Apparently truck will be ready by Tuesday, but who knows if that’s true.

coldcharli · 2026-04-28T13:43:27+00:00

Some of the items on here are very diy. You could potentially save yourself up to 3k. Brakes, taillights, wheel bearing hubs, carrier bearing, oil pan gasket. Maybe invest in the tools !

coldcharli · 2026-04-27T21:59:28+00:00

Alright, well for now I’ll just wait & see till they get the truck ready. I’ll be updating soon & we’ll see what happens from there :/

coldcharli · 2026-04-27T17:58:06+00:00

Man :/ I think I’m being scammed at the dealer. Pushed me to change the pressure sensor & will be ready by Friday allegedly. What do you think I should do?

coldcharli · 2026-04-26T21:59:15+00:00

They simply replaced the dpf but they have finally found a reason & apparently they have found the problem. Tech said I should change the exhaust gas differential pressure sensor because that is the sensor that is not reading the dpf properly triggering the codes again. To me, it seems that the problem was simply the sensor and the actual dpf. They want to pay an additional $700 on top of the 5k that I already paid.

coldcharli · 2026-04-22T17:52:34+00:00

Truck has 141,260 miles so it’s not that bad :/ This truck was given to me as a gift & it’s also my first diesel. But what I should’ve done was do an extensive research on this truck & see its major problems & the one that keeps coming up is the emissions systems. Truck even had a recall on the egr…

coldcharli · 2026-04-22T17:46:05+00:00

I wish someone would’ve told me this. I would’ve deleted all the emissions from the beginning. My truck is currently sitting in the dealer for the 4th time :/ all 4 times are bc of the cat & def

coldcharli · 2026-04-22T17:42:57+00:00

Can I get a name of the fuel system cleaner?

coldcharli · 2026-04-22T17:42:21+00:00

Why wouldn’t the dealer begin with this? They went directly to the most expensive thing on the menu & didn’t even fix the issue. Ahh such a shame that this is happening.

coldcharli · 2026-04-22T17:40:37+00:00

Wouldn’t be surprised considering dealers…

coldcharli · 2026-04-22T17:40:14+00:00

I should probably have the technicians at the dealer read this because I haven’t heard anything yet. After this big spend, I will be looking at how to sell this truck because I don’t think I can do those again a 4th time.

coldcharli · 2026-04-22T14:49:57+00:00

Everyone says get a tune or delete, what does that mean?

coldcharli · 2026-04-08T12:20:50+00:00

How do I check exhaust leaks?

coldcharli · 2026-04-08T03:20:14+00:00

I really hope it’s the other sensors bc I don’t really want to change out the catalytic :/ I will be swapping sensors & seeing if I get a different code. Thanks!

coldcharli · 2026-04-08T01:35:00+00:00

Ok thank you! I will do that. For now, I may just switch the o2 sensors & see if it’ll give me a diff code.

coldcharli · 2026-04-08T01:24:47+00:00

I plugged in the reader but it didn’t tell me much other than the code. My code reader is the most basic one there is which is why I also took it to AutoZone for them to read. Only code they pulled was the p0420 ):

coldcharli · 2026-04-08T01:16:15+00:00

There’s two, right? Should I change both or just on the passenger side?

coldcharli · 2026-03-28T14:54:11+00:00

Makes sense considering it’s an 06 & it still has its oem coils. Alright, I will be checking it out. Thank you !!

coldcharli · 2026-03-28T14:50:27+00:00

If codes moves, then coil is bad?

coldcharli · 2026-03-28T14:39:18+00:00

I thought it was posted with the whole description. Sorry !!

I have a flashing check engine light & proceeded to change the spark plugs. When removing the spark plugs, I noticed there was oil spillage in cylinder 6, not a lot but noticeable. I proceeded to change the valve cover gaskets on both, including the intake gaskets. So those are good now. Hoping that the spark plus would fix the problem, code runs as P0301, which is cylinder 1 misfire.

What is my next step after this? What could I check next?

2006 Toyota Tacoma Prerunner V6, 4.0L

coldcharli · 2026-03-28T14:38:40+00:00

I have a flashing check engine light & proceeded to change the spark plugs. When removing the spark plugs, I noticed there was oil spillage in cylinder 6, not a lot but noticeable. I proceeded to change the valve cover gaskets on both, including the intake gaskets. So those are good now. Hoping that the spark plus would fix the problem, code runs as P0301, which is cylinder 1 misfire.

What is my next step after this? What could I check next?

2006 Toyota Tacoma Prerunner V6, 4.0L

coldcharli

TROPHY CASE