Check Engine Light
Thread Starter
Cruising
Joined: Sep 2006
Posts: 12
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Check Engine Light
2003 50th Anniversary Coupe, 6 speed manual, purchased brand new. The exhaust system shown is exactly like mine. I have a CEL code: P0430=catalyst efficiency below threshold. It could be the downstream O2 sensor or the cat. I know the two oval "canisters" are cats. Does anyone know what the smaller round "canisters" are at the front of the exhaust? Are they cats, mufflers, resonators, or WHAT???
It is stone stock and I want to keep it that way. I DO NOT want to remove the cats or add headers. This is a daily driver and I simply want to pass my state's emissions test or they will make me a daily walker. Thanks.
Melting Slicks
Joined: Sep 2011
Posts: 2,258
Likes: 544
From: Appleton WI
I agree that it is the left side. You can have someone hook up to the computer to determine which is bad (cat or sensor). If the cat is bad, the 2nd O2 sensor will track the 1st sensor nearly identical. My cat was toast after 250k miles. I had the rear O2 sensors tuned out.
Last edited by 3sACROWD; Oct 13, 2017 at 01:49 PM.
Thread Starter
Cruising
Joined: Sep 2006
Posts: 12
Likes: 0
The "pup" cats were eliminated on the LS6 when they bumped the hp to 405 in 2002.
I agree that it is the left side. You can have someone hook up to the computer to determine which is bad (cat or sensor). If the cat is bad, the 2nd O2 sensor will track the 1st sensor nearly identical. My cat was toast after 250k miles. I had the rear O2 sensors tuned out.
I agree that it is the left side. You can have someone hook up to the computer to determine which is bad (cat or sensor). If the cat is bad, the 2nd O2 sensor will track the 1st sensor nearly identical. My cat was toast after 250k miles. I had the rear O2 sensors tuned out.
Melting Slicks
Joined: Sep 2011
Posts: 2,258
Likes: 544
From: Appleton WI
I would assume the pup cats have the same materials in them as the larger cats. They are just closer to the manifolds so they heat up faster. They likely can fail as well.
Instructor
Joined: May 2006
Posts: 202
Likes: 16
2003 50th Anniversary Coupe, 6 speed manual, purchased brand new. The exhaust system shown is exactly like mine. I have a CEL code: P0430=catalyst efficiency below threshold. It could be the downstream O2 sensor or the cat. I know the two oval "canisters" are cats. Does anyone know what the smaller round "canisters" are at the front of the exhaust? Are they cats, mufflers, resonators, or WHAT???
It is stone stock and I want to keep it that way. I DO NOT want to remove the cats or add headers. This is a daily driver and I simply want to pass my state's emissions test or they will make me a daily walker. Thanks.What you want to see is a high frequency on the front O2s & closer to a flat line on the rear O2s. New clean O2 sensors will likely be more responsive than old ones. I would NOT replace a rear O2 for a PO420/430 code for this reason.
The atached photo shows Graphs from B1&B2 O2s. Bank1 (top 2graphs) is working well, but B2 (bottom 2) cat is DEAD
Last edited by JBB; Oct 14, 2017 at 10:30 AM.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Last month, I got a P0430 code. I had driven the car about 12 miles to a car show. Spent most of the day there with the engine off. On the ride back home, the CEL came on. Checked the codes and the P0430 showed up as a current code.
I needed gas for the car so I got it filled up (CEL still on). I decided to clear that code and take it for a ride and keep the engine RPM at mid-range. Drove on the freeway using 3rd and 4th gear only for about 30 miles. I kept Rpm to around 2500 to 3500 as much as I could. Got back home and no CEL!! Still hasn't come back even after a 150 mile trip.
So I wonder if that higher RPM driving I did helped to clean everything up both inside the cat and the bank 2 sensor? Do short trips tend to cause clogging the car or getting carbon on the O2 sensors?
I needed gas for the car so I got it filled up (CEL still on). I decided to clear that code and take it for a ride and keep the engine RPM at mid-range. Drove on the freeway using 3rd and 4th gear only for about 30 miles. I kept Rpm to around 2500 to 3500 as much as I could. Got back home and no CEL!! Still hasn't come back even after a 150 mile trip.
So I wonder if that higher RPM driving I did helped to clean everything up both inside the cat and the bank 2 sensor? Do short trips tend to cause clogging the car or getting carbon on the O2 sensors?
Instructor
Joined: May 2006
Posts: 202
Likes: 16
Yes. In the old "2 speed emissions testing" we used to precondition certain vehicles (hold at 2000 RMP for 2 min) to make sure they got a fair shot at passing. The flames clean the front O2s & burn the soot out of the cat.
Last edited by JBB; Oct 16, 2017 at 10:20 AM.
