My friend has a 2000 Honda Civic Si. He first installed an aftermarket intake when he first bought it. Recently, he added aftermarket header and exhaust system. All was fine. Then he added a Hi-Flow Cat. After a week, he then got the notorious Check Engine Light. He checked tha codes and said first one he got was "Insufficient Amount in Threshhold" then he got "Low Voltage" (this is what he told me???). Next, he tried putting aluminum foil around the o2 sensor in the cat and that worked for 1 week. He has emissions and is to the point of stripping everything off, going back to stock. Also, someone recommended switching to OBD1 but he doesn't want to go that route.

I'm trying to find other options so he doesn't go back to stock! I heard putting a resistor in place of tha o2 would work but I also heard it's a 50/50 shot. I did some searching online and couldn't find anything posted on any domain.

Any help would be most appreciated!

 

pull the hi flow...then...re install cat converter...pass emissions.

THe only thing thats making it fail is that "hi flow" cat

you can re install the hi flow cat after emissions

 

It would be awesome if you guys knew someone with an actual OBD2 scan tool to have the codes checked with it. the flashing light code check is too vague for OBD2 codes dealing with anything emissions related.

If you can get me some "P codes" like P0401, P0420, etc. etc. we can all help you better.

Having said that I'd almost guarantee he's throwing the ever famous "catalyst efficiency below threshold" code because of that test pipe. I know of a few things he can do to fix it:

Buy an o2 simulator for the sensor in the test pipe

or

Reinstall the OE convertor and possibly a new secondary o2 sensor (if his is ruined from the test pipe) until the car passes, then go back with the test pipe.

I'm not a huge fan of test pipes on OBD2 cars because they always throw codes and the perfomance is usually no better than with a larger diameter convertor.

 

Koo and thanks.

He'll plug it up this weekend to get tha actually codes from an OBD2 scan tool.

He just said in the beginning he got the code for "catalyst efficiency below threshold" but now he's getting "low voltage".

Until he gets the codes from a reader, that's all I have.

Any thoughts?

 

Well I assumed right about the convertor - swap the stock one back in with a good secondary o2 sensor, or buy a simulator and hope the emissions guy can't tell a test pipe from an actual convertor.

The "low voltage" might be in refernce to the secondary o2 sensor if he doesn't have one hooked up.

 

Thanks alot dood! I'll relay the message and hopefully tha next post has good news!