At my limit with exhaust

[Nelsonmd]

So I am struggling with trying to fix my exhaust, and I am about ready to give and pay up for a shop to do this for me.

I have a P0420 CEL, and have replaced the rear O2 sensor already. I have checked the heating elements on both rear and front O2 sensors and they are fine. I don't know of a way to check the waveforms without taking it into a dealership and paying up the nose for it.

I have searched for an exhaust leak in the manifolds, and at all the other joints and around welds and can't find any (not that I am that certain as I couldn't check real well). There is alot of rust on the flanges, and it certainly looks like they could be leaking, but I can't feel any air leaking out when the engine is running.

Does anyone know a good way to perform any of the following without expensive equipment?

Check the waveform/functionality of the O2 sensors.
Check the functionality of both of the Cat's (or just determine which is bad).
Check for exhaust leaks (preferably without burning myself).

I am stressed about this because I only have 10 days left on the temp plates and need to get this thing inspected and registered.

 

[yc4runner]

As for the exhaust leaks, if you see any black sut like stuff around any of the welds or joints you got a leak.

 

[Gerdo]

Since you replaced on O sensor I would replace the other one also. What else could cause your code?

 

[Nelsonmd]

As for the exhaust leaks, if you see any black sut like stuff around any of the welds or joints you got a leak.

Yeah, I looked for soot, but couldn't find any. I even bought one of those little extendo mirrors to check out the hard to reach manifold pipes. Rusty like crazy, but no soot.

The front sensor (which I havn't replaced) looks pretty new, I don't think it is the problem.

How difficult would it be for me to pull of both old Cat's and replace them myself? Can I even do that, or do I need a shop that can bend pipe?

 

[Gerdo]

If you are going to replace your exhaust yourself you should use a pre-bent kit. that shouldn't be too hard. Don't over tighten the clamps, you will actually cause leaks by deforming the tubes.

If you are still looking for leaks you can buy a cheap stethoscope at the auto parts store and take a listen for leaks.

 

[Nelsonmd]

The FSM says to check for "gas leakage on exhaust system". What does this mean?

 

[quicksilvr]

The FSM says to check for "gas leakage on exhaust system". What does this mean?

It's toyota speak for: make sure all the flanges are tight and clean, and make sure there are no holes in anything. Basically telling you to check for exhaust leaks....which you already have.


Sucks that the downstream O2 sensor didn't fix your problem. I think you're stuck with having to get new cats. You could take it somewhere and have two new Magnaflow universal cats installed. But that's still a slight risk because they might not be stout enough to keep the CEL off.

Personally, I would just install ONE new Magnaflow cat, and then use this: Rear Sensor Simulator - Underdog Racing Development


You could probably JUST use the simulator to pass inspection...but then you still have bad cats to take care of in the future.

 

[RAB]

Just reset the ECU before you go to the emission place. Trust me your truck is running clean enough to pass. To reset the ECU, just disconnect the negative cable on the battery.
As for the P0420, I'm lost as well. I did the following and got it to go off for awhile, but it intermittently comes on.
1.) Cleaned the mass air flow sensor.
2.) Replaced the spark plugs, I needed to do it anyways.
3.) Cleaned the throttle body.
4.) Replaced the rear 02 sensor, on CA emission models the sensor before the cat is a/f ratio sensor.

 

[Nelsonmd]

Just reset the ECU before you go to the emission place. Trust me your truck is running clean enough to pass. To reset the ECU, just disconnect the negative cable on the battery.
As for the P0420, I'm lost as well. I did the following and got it to go off for awhile, but it intermittently comes on.
1.) Cleaned the mass air flow sensor.
2.) Replaced the spark plugs, I needed to do it anyways.
3.) Cleaned the throttle body.
4.) Replaced the rear 02 sensor, on CA emission models the sensor before the cat is a/f ratio sensor.

See, I thought about that, but can't they tell that all the checks haven't been done since the code was last cleared? I think I read somewhere that when you clear the codes, it also clears the engine check data, so they can tell that all the checks haven't been done since the last clear. Or does pulling the battery cable not erase the data?

I plan on cleaning the MAF and replacing the spark plugs, but I figured I would fix the CEL first as it is my top priority. Maybe I should do those now anyway.

I heard on here that all 4runners 2000 and up are california emissions, does that mean I should have put a california emissions rear O2 sensor in?