cboisits

My check engine light has been on for the past week. When I hook up the SCT2,it displays the following:

PO430
CAT SYS
EFF BLW
THRE2

I did my research to find out that it means "catalytic system efficiency below threshold ". After doing my research I also read something about bank 2 / dual? I have Magnaflow hi flow universal cats. 40k miles on my car. What do I do about this?

howarmat

clear the code and it might not comeback

Jersey Stang

It's common with hi-flow cats. The rear o2's won't effect performance, that's why they are usually turned off when you get a tune. Howarmat is right, clear the CEL and it shouldn't come back.

cboisits

Thanks guys.

tx_zstang

It wont go away. Clearing the code will get rid of it for a few drive cycles, then it will come back.
I have magnaflow high-flows, too, and have the same issue.
But usually, it starts with P0420, bank one, and a few drive cycles later, the P0430 will come up too.

Technically, the issue is the values read from Mode 6, Pid 21 and 22. The 'counts' are accumulated over each drive cycle, and there's a threshold limit as to the upper max count value. When your count goes over that, it throws the code.

Functionally, the issue is because the high-flow cats are not producing the proper damped/altered signal that normally-operating cats will produce.
So how do you fix it? I know of two ways, neither of which I've yet tried.

One is to have the rear O2 sensor backed out some from the pipe, so that the sensor end does not stick into the pipe very far or much at all. using a modified bung or spark plug spacer ring can help do that. i know of one person locally who has done this and it solved his problem.

Another solution, one that I'm going to try soon, is to modify the rear O2 sensor circuit per a modification that I found somewhere online, using a 1microfarad cap and a resistor of I think like 10K ohms. The circuit alters the response of the signals produced by the O2 sensor to shift them to either a higher or lower voltage and to reduce the amplitude of the spikes. This reduction of amplitude variations should solve the issue.

I'll be doing the latter and seeing how it works.

But on the bright side, look at it this way: this 'problem' is , IMO, a testament as to how free-flowing the high-flow cats are!

howarmat

actually you can just have the O2s shut off completely with a tune and then you dont have to worry about it at all