KKu77

I got this code the other day. What does it mean?

P0420 TWC System Low Efficiency Bank 1

I reset it and haven't seen it since.. but i'm curious now.

ersatz928

I think it refers to the efficiency of the catalytic converter (how well it converts bad stuff to good stuff, chemically speaking) That is what the second oxegen sensor, located after the cat, is for. It compares the cat output to the cat input (from the Ox sensor in front of the cat) If the cat efficiency drops too much, as it gets older, the Check engine lamp will come on, so that the cat is replaced. Bank refers to which cylinder bank and catalyst unit. (left or right side)

speedyc5

Mine gets P0420 and P0430 at the very same time, so I doubt that it is really related to the CATS. On my car I would guess it is something ahead of the CATS that is common to both banks.

:smash: :smash:

SFVetteman

P0420 refers to the rear O2 sensor that is behind the driver side catalytic converter. P0430 is the rear O2 sensor on the passenger side. The PCM at idle tests to see if the converter is working by changing the Air Fuel ratio from rich to lean and from lean to rich and measures the response time of the front and rear O2 sensors on each bank. The code sets when the response time is too long which indicates a reduced oxygen storage capability of the converter.

If no other codes are set then the problem is because of exhaust system leaks or damage, burnt or damaged rear O2 sensor wires, loose rear O2 sensor mounting or a bad converter. If you clear the code it doesn't come back then I would not worry about it :cheers:


[Modified by SFVetteman, 7:46 PM 2/19/2004]

KKu77

Could this have anything to do with the outside temperature being colder than normal and the cats just not warming up in time? Of course, i'm in Houston and the computer threw the code when it was only about 55-60 degrees, so that theory may be bad.

Can a bad batch of gas cause something like this?