Code P0421 and the AOS
08-03-2017, 08:22 PM
#1
Drifting
Thread Starter
Code P0421 and the AOS
As I was dropping my '06 CS (32,500 miles) at the shop to have my internal engine track mods done the CEL came on, Code P0421, right bank catalytic converter. Tech found the original AOS appeared to be bad and that could have thrown some oil into the cat. Changed to a Motorsport AOS and so far after 70 miles no CEL so fingers crossed that the bad AOS was the problem.
EDIT - 10 miles later, at 80 miles, CEL back on, Actron OBD II scanner arriving today so I can see if it is the cat. Crap!
EDIT - 10 miles later, at 80 miles, CEL back on, Actron OBD II scanner arriving today so I can see if it is the cat. Crap!
Last edited by jsabatini; 08-04-2017 at 10:22 AM.
08-09-2017, 09:16 AM
#2
Intermediate
I've been having the P0421 code intermittently as well. I swapped O2 sensors side to side, and no change, so I'm fairly certain the code is due to the CAT failing. Affordable CATs are available from Magnaflow (~$450, I think). Does seem a bit odd for it to fail at only 35k miles though.
Also, I have read on Planet-9 that early CS's had a more stringent threshold for cat warmup efficiency and this was relaxed a bit in later years. Supposedly you can get your ECU reflashed with an 07+ tune to have the more relaxed threshold. However, I talked with the Porsche dealer and they had never heard of this, so who knows...
Also, I have read on Planet-9 that early CS's had a more stringent threshold for cat warmup efficiency and this was relaxed a bit in later years. Supposedly you can get your ECU reflashed with an 07+ tune to have the more relaxed threshold. However, I talked with the Porsche dealer and they had never heard of this, so who knows...
08-11-2017, 09:23 AM
#3
Drifting
Thread Starter
Plan B: Called my other local shop and they mentioned this O2 Spacers for Catalytic Converters.
http://www.fabspeed.com/universal-90...ic-converters/
Taking Pepper to the shop later today to see if this gets rid of the code.
EDIT to add, ignore the link to the FabSpeed spacer above, go with the Soul Performance spacer and save over 60% for what looks identical.
https://soulpp.com/product/universal...tic-converter/
http://www.fabspeed.com/universal-90...ic-converters/
We've taken our O2 spacers a step further. The factory ECU compares the readings from a pair of oxygen sensors to measure the effectiveness of the catalysts. When a high-flow cat or catbypass pipe is used the exhaust gases reach the O2 sensor faster and uncleaned, leading to high chances to throw a CEL. Our O2 spacers retract the secondary oxygen sensors from the direct flow of gases, restoring the balance that the ECU requires when using aftermarket catalysts or catbypass pipes. The high quality built in catalysts scrub the exhaust to further reduce the chance of a CEL. Two fitting options and the two piece design allow for adjustment to get best possible fitment and results.
EDIT to add, ignore the link to the FabSpeed spacer above, go with the Soul Performance spacer and save over 60% for what looks identical.
https://soulpp.com/product/universal...tic-converter/
Last edited by jsabatini; 08-11-2017 at 03:06 PM.
08-14-2017, 10:57 AM
#4
Drifting
Thread Starter
And the fun continues, curious to see if the CEL would come on again after the spacer install I took Pepper for a drive yesterday, and sure enough, at 80 miles since the last reset, CEL. This time codes P2196 and P2198, the O2 sensors in front of the cats. The spacers went on and moved the O2 sensors behind the cats, the O2 sensors in front of the cats were not touched. 
08-15-2017, 03:53 PM
#6
Intermediate
Give it time. If it is, in fact, the same issue as my car, it is often set off by slow, low-rpm driving and it can sometimes stay off for hundreds of miles before cropping up again.
08-15-2017, 04:15 PM
#7
Drifting
Thread Starter
More importantly, what is the issue your car has?
Thanks!
Trending Topics
08-15-2017, 04:18 PM
#8
Intermediate
Well, I've swapped O2 sensors side to side (both fronts and rears), and the code did not switch sides, which leads me to believe the only thing left to replace is the cat. Since it's not a real issue, I've just let it be and keep clearing the code when it crops up.
08-17-2017, 09:31 AM
#9
Rennlist Member
