DaleW

2000 teggy, 117,000 miles. We recently purchased this car.
Previous owner has receipts for 02 sensors and catalytic converter,
but really, these could be bogus to get him past his last state emissions test.

So just now the car CEL goes on, and the code is P0420, catalytic converter below efficiency threshold.

I googled the code, and youtube has a video by scotty killmer (he has many) where he suggest these steps:
First try:
1/2 tank gas, 1 gallon lacquer thinner, 150 miles at highway speed.

Then try:
remove catalytic converter, soak in water with dishsoap overnight to clean.

Then:
replace catalytic converter.


I'd like to think if either of the o2 sensors were bad, they would throw a different code. Right?

Anybody here do the lacquer thinner? Scotty says he has been doing that for 30 years, and has not melted an injector pump or any other fuel system components.

Naturally this has to happen right when we get the paperwork from the state to have the car emission tested.

As a side note, I found a product on Amazon called 'Guaranteed to Pass' by CRC.
Anybody ever give this a try?

Thanks, Dale

rick_rabies

lacquer thinner in the engine? no, use seafoam if anything.

if the cat is old its prolly clogged.

johnjw

Do you have emissions testing where you live? There are a few ways to trick the ecu if not. Your P0420 is catalyst efficiency. When this code sets, it usually means that the primary and secondary O2's are following the same mV rise and fall. NOT usually that the cat is plugged.

I would not try any of the tips/hints you have read. Or CRC's stuff, as this is prob a temp fix by slowing down the secondary O2. If you don't have emissions testing in your area and the previous owner just installed a cat (prob aftermarket, reason for CEL), I would run a sparkplug non-fouler in the secondary O2. I know this means that it will not monitor the O2 anymore but it does the trick. If the cat is new it prob is functioning right, just not within the ecu's range (2O2s is prob switching too fast).


edit; I just read that you do have emissions............ disregard lol

Former User

P0420 usually means the cat is bad, but it can also be caused by an exhaust leak. But before you do anything, reset the ECU to see whether the same code returns.

Invariably, the cat is killed by the engine running too rich. This condition is most often caused by misfires resulting from the failure to do regular tune ups.

DaleW

Thanks,
I did reset the CEL. I should add that the car is used for short trips, 3 miles to school and 3 miles back. Sheesh, is the engine/cat even hot by then? Perhaps a nice 20 min run on the freeway to heat up the cat?

I have read where you can use a multimeter to test the voltage from the O2 sensors. They should fluctuate in a certain range when hot.

garagedna

You do not check voltage on the o2 sensors but you check the ohm resistanse by connecting the multimeter to the two black wires if its with four wires. Usually that code is the rear o2 sensor

hybridmiklo

Wrong!!! You do check voltage from o2 sensors!!! You do not check with resistance unless you are checking the grounds. The primary o2 should fluctuate from approx 300 mv to 800 mv and should do so every 100 milliseconds.

The secondary should not switch as often as the primary, actually is should not switch much at all as all it does it monitor the oxygen coming out of the cat. If it is always reading oxygen most likely the cat is no long efficient.

The only catch is to read the o2 sensor you need something thats faster than a multimeter. You need to use a scope. The primary should avg 450 mv.

DaleW

I did connect up my Actron AutoScanner cp9575 to the Teggy. I can select 'live data' and it will give me the volts from the the two sensors as the engine is running.

With engine off, both o2 sensors read 1.275

just when fooling around, not with hot engine, o2s11 was .095 to .115, and o2s12 was .25 to .31
(doesnt that seem a backwards? remember, cold engine, I think closed loop)

But these reading are meaningless because the engine was not hot, I was just fooling around in the parking lot at work one lunch hour.

The CEL is off. all Monitors on the scan tool read OK, but not 'catalytic'. Catalytic reads INC because the car has not gone thru proper drive cycles since I set the CEL off.

I plan on taking the car in to be smog tested. If they refuse to test because of the one incomplete moniter, I will just drive it until the catalytic moniter gets a change to do its readings. If I get time, I will get the car upto temp, and see what the two o2 sensors read when hot.

Thanks

Dale

civicsirebuild

have you taken the cat off to see if its hollowed out? if you dont want to buy a new one, i second the spark plug non fouler trick, one inside the other works great, as long as the cat isnt actually clogged.

DaleW

I have not taken the cat off (yet). The dim-bulb previous owner replaced the cat with one that still bolts on in front, but then welded out the output end. I can cut it, and may end up doing that.

But, one step at a time. If it passes the state test, and if the CEL stays off, I will most likely not do a thing.

I had never heard of a spark plug non-fouler until now. I googled it, and it seems like a clever idea.

DaleW

So far (two weeks) and the CEL has stayed off. I was checking the status of the 'catalyst moniter' probably every other day with the Actron Scanner. The status was INC (Incomplete, meaning not enough drive cycles since turning off the CEL).

My son took the car in to be smog tested. I was hoping to find out if Wisconsin would let us pass with one incomplete monitor. The car passed, and wouldn't you know it, the car gone thru enough drive cycles to set the catalyst monitor to OK.

So I am glad the car passed, but I still don't know if WI would pass with one incomplete monitor. My son told me the car in the next bay failed, and he overheard the state employee telling the owner that the car had too many incomplete monitors, and he needed to drive the car some and bring it back. Wish I knew how many incomplete monitors it takes to fail a car.

I pulled all four spark plugs. Normal wear, nothing to indicate a rich engine condition. I was happy with that. So whatever. I got two years until the next test.

Thank you all for your answers.

Dale