I failed my emission test with the P0430 code- catalyst efficiency below threshold(Bank 2). I don't know what to do first.

 

juwels, this is normally due to a bad O2 sensor. So, you are most likely looking at doing the bank 2 upstream sensor and seeing where your codes go from there.

An option that you can try that while it does wonders, it may or may not help your situation is to run a can of Seafoam through your engine. You are not going to add it to your gas. You are not going to add it to the oil. You are literally going to suck it into the intake and let it go through that way. If you look on top of your engine, there is a line that you can remove that runs over to the brake booster. You are going to remove this line and fill the hole in the intake with a thick wall vacuum line (may need to build up the end with a little bit of masking tape to get a good seal). You do all of this with the engine off but the engine already up to temperature.

With the help of a second person, have them start the car as you keep your thumb over the end of the rubber hose (needs to be about 4 feet long). Remove your thumb from the end of the hose and immediately stick the hose into an open can of Seafoam. The person inside the car is going to have to get on the gas to keep it running. THE CAR IS GOING TO SMOKE!!!!!!!!!!! Once you get about 1/3 of the can sucked into the engine, let the engine die. The engine is going to suck in a little more fluid and leave you at about 1/2 a can. Pull the hose from the can if you get to 1/2 if it is still sucking fluid in.

Let the car set for 5-10 minutes (the longer the better, but not so long as the engine starts to cool down). Restart the car and get it to the point that it will maintain idle (you will need to put your thumb over the end of the hose again). Once the car can maintain the idle by itself, remove your thumb and suck down the rest of the can of Seafoam (again, having the person inside the car keep the engine running). Once the can gets empty, pull the hose from the can and place your thumb over the hose. Keep giving the car gas until it can idle by itself. Turn the engine off and reinstall the hose that was initially disconnected.

At this point, you will need to go for a drive. It will take another 5-10 minutes, but the exhaust will stop smoking. Manually controlling the gears and getting the engine RPMs up in the 4-5000 RPM range will help clear things out faster.

Did I mention that the car is going to smoke A LOT!!!!!!!! So, you will want to find a fairly remote place to do this so you don't smoke out your neighbors.

This may or may not fix your problem. The Seafoam will help break up the carbon that is on the O2 sensor and inside the cat and hopefully improve its efficiency. But, no promises on this.

If the Seafoam doesn't fix things and installing new O2 sensors doesn't help, then that leaves you with replacing the cat on that side.

 

I have the same code and am having difficulty determining which O2 sensor is possibly to blame.

Most places online point me to the downstream sensor, but Thermo mentioned the upstream sensor. I believe Thermo knows his stuff, so I'm not sure if it was a typo here or what. Hopefully this can be clarified.

 

juwels/Lub, ironically, it can be either one (upstream or downstream). This is where having a code reader/computer that can look at real time data will be the saving grace with a problem like this. In short, during normal operation, you should be seeing 3 sensors all reading about the same (around 0.5V) and the last one most likely reading 0.0V. The one reading 0.0V is going to be your bad sensor.

Some members have "corrected" the problem by getting some extension sleeves for the downstream sensors so they don't see as much of the downstream cat exhaust which seems to make things better too. But ,I would start with the real time data and go from there.

 

Instead of at the vacuum port for the brake booster, wouldn't it be better to do this at the vacuum port just behind the throttle body? This way the Seafoam would enter both the upper and lower channels of the intake (to be distributed to both Bank 1 and Bank 2 of the motor)? If you go through the vacuum port of the brake booster, it will only be going to one Bank of the motor..

Additionally, seafoam makes a top end motor cleaner spray (about $15) that can be used instead of the liquid intended for adding to the fuel or crankcase. This might be easier to do through the vacuum port since it's a spray.. of course, you would have to plug the open vacuum port in a manner that would prevent a vacuum leak, but allow the insertion of a straw to spray the Seafoam Top End Cleaner inside the port of choice.

Keep in mind, if done directly through the throttle body it will clean the throttle body and go to both Banks 1 and 2, as well. To do this you would remove the throttle body side of the accordion hose from the breather.. insert the spray straw that comes with the can, on the side where the butterfly opens in.. And reattach and secure the hose back to the throttle body to keep straw in place.. start the car and keep it about 2,000 rpms (use a helper or improvised way to maintain rpms).. and spray until the can is empty.. this will clean the entire top end to include the O2 sensors..