Need Help with O2 sensor codes!!!!!------
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 4,809
Likes: 236
From: Utah
Need Help with O2 sensor codes!!!!!------
I have installed GHL long tube headers with GHL Bullet exhaust. I also have a Vararam. The problem is the check engine light comes on intermittently, usually after 1-1.5 hours of operation. I've checked the display and get 0420 H C. Can Catalytic converters be defective? (I have R T metal matrix high flow cats). Would a leak cause this? Any other ideas or input would be appreciated. 
Drifting
Joined: Jul 2002
Posts: 1,484
Likes: 0
From: Morgan Hill Ca.
This code says the catalytic converter is not operating at expected effeciency.
This is determined by the PCM compareing Bank 1 HO2S#1 to Bank 1 HO2S#2. # 2 HO2S should be less active than #1. The PCM has detected activity outside the acceptable range for an extended period of time.
You already checked for leaks. so check the HO2S connectors are tight and wires not touching anything. Make sure they are in the bungs snug with no leaks. Pending anything else, you may well have a bad CAT. PCM does the same check on BANK2 and your Bank 2 is passing. It is a lot of work but you could swap the CATS to check.
Where in the system did you mount your CATs. Sometimes when they put them after the X pipe they have a hard time getting up to temp.
My vote is a defective cat. Also double check the wires left to left and right to right. A lot of people get them swapped on a header install.
Could be a bad sensor#2 but then it should fail the startup test which is a range test and it would throw a different code. You could just go with Sims and eliminate the rear sensors completely.
This is determined by the PCM compareing Bank 1 HO2S#1 to Bank 1 HO2S#2. # 2 HO2S should be less active than #1. The PCM has detected activity outside the acceptable range for an extended period of time.
You already checked for leaks. so check the HO2S connectors are tight and wires not touching anything. Make sure they are in the bungs snug with no leaks. Pending anything else, you may well have a bad CAT. PCM does the same check on BANK2 and your Bank 2 is passing. It is a lot of work but you could swap the CATS to check.
Where in the system did you mount your CATs. Sometimes when they put them after the X pipe they have a hard time getting up to temp.
My vote is a defective cat. Also double check the wires left to left and right to right. A lot of people get them swapped on a header install.
Could be a bad sensor#2 but then it should fail the startup test which is a range test and it would throw a different code. You could just go with Sims and eliminate the rear sensors completely.
Last edited by BlueDragon; Feb 4, 2005 at 01:10 PM.
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 4,809
Likes: 236
From: Utah
I checked my clamps and made sure they were tight also checked the O2 sensors and tightened them. Cats are in front of the x-pipe, so I think they are getting to the appropriate temp. The wires looked ok and They were not mixed up. If this does'nt work I'll change the cats. Thank you for the suggestions Blue Dragon! 
