Hi all, I caught the P0420 Flu. I've been doing my homework and I don't know how to fix this.
The three main symptoms, I don't have them:
1. Sulfur/Eggy Smell. My exhaust smells like an exhaust.
2. Loss of power/response. I press the pedal, car goes VRROOOOMMMMMM
3. Rattling Exhaust/Cat. Converter. Nothing really rattles, everything sounds like it should.

Although, I will say that there is water? coming from my exhaust whenever I put the pedal down. Could that throw a P0420?
I was planning on running some Sea Foam through the cat, as seen in this video:
Before I do this though, I'm gonna get under the car and make sure the O2 Sensors are all tightened/in good condition. I did have a P0147 in which I fixed by replacing the O2 Sensor for that code.
Anyone else have any solutions or a way for me to get to the Tootsie Roll Center of this Tootsie Pop of a problem code?

 

Most likely issues:

O2 sensor failure or connector/wiring issues
Faulty ECT sensor
Exhaust leak
Cat failure
Timing/ignition issues/misfires
Rich fuel mixture

If you have cat failure you need to determine and correct the root cause. A few methods of testing the cat:

Measure back pressure at an O2 sensor port in front of the cat.
Measure the temps in front of and behind the cat
Tap the cat and see if it rattles
Watch the O2/air fuel sensors in live data

George

 

Say, my car does have trouble starting up. Like, it'll start up on the first key turn but it'll lag a little. If that makes sense
It'll go drdrdrdrdrdrdr-VROOOOMMMM.... rather than starting up all the way.

Recently I brought the battery back to life, could that be something that could cause a P0420? I haven't charged the battery all the way, just enough to get it to come back to life.

 

Having a healthy battery, charged properly is fundamental to many of the trucks systems. This should be straightened out first. IDK if low voltage can cause this code.

George

 

Right, next time I have the cash to do so, I'll invest in a good battery tender.
Hopefully that's the issue here, trying to start with the least expensive fixes.

But it still begs the question about the water. I looked it up and saw if white smoke comes out, it could be a damaged head gasket.
Its not a laarrge amount of water but I think that I'll let it run for awhile and see if water keeps dripping out before ruling out the gaskets.

Feeling like Sherlock Holmes with this damn Blazer now.

Source for Water Thing: https://mechanics.stackexchange.com/...g-from-exhaust

 

Quite normal to get drips of water out of the exhaust pipe for several minutes after first starting due to condensation within the exhaust system, especially when air temps are cold.
So yeah, let it run for a good five minutes and then check. Also you could remove the radiator cap prior to starting engine and then with engine running look into radiator, check for air bubbles.
And another prior to starting engine, pull oil dipstick and check to see if coolant in the oil. Also check after engine has run, see if dipstick has "chocolate milk" on the end.

 

Inexpensive places to start:


Is the fluid level dropping in coolant system?

what do the plugs look like?

if you have a scanner, looking at the O2 sensors in live data

tapping on the cat to check for loose pieces

checking the ECT sensor.

if you have an infrared thermometer, checking the cat input and output temps

checking compression

as mentioned, the condition of the oil, bubbles in the radiator


George

 

A couple questions Cinnamon:

A) Does the truck drive ok once you get it going?

B) Do you have the time/money to fix this properly, and to go through all the diagnostics (lol even the incredibly unlikely/ridiculous ones that were previously mentioned)?

Or...

C) Do you just want the light to go away and be happy, because IMO most likely your catalyst is fried from the dead misfire you had back in July?

 

Please don't run Seafoam through it. Read https://en.wikipedia.org/wiki/Catalytic_converter specifically about damage and diagnosis. Are the people in the video counting on the extremely high converter temps that adding a lot of hydrocarbons (like seafoam) would provide, in order to clean off the catalyst surfaces? Sounds like a really good way to turn your converter into a Chernobyl disaster.

Beware of the easy fixes on the Internet - most are BS.

The guy in the video is not the sharpest tool in the shed. If you read his responses to his comments he speaks of using the "hole" can of Seafoam.

 

Honestly, George has helped a lot of people here. If you disagree you should do it in a much nicer way. Don't confuse your opinions as always being fact.