Occasional codes after Header install
Thread Starter
Race Director
Joined: Jul 2004
Posts: 16,795
Likes: 62
From: Lake Havasu City, AZ
Occasional codes after Header install
I installed American Racing headers with high flow cats.
3 times in the past week the check engine light has gone on and the codes are P04020, P04030
They speak of inefficency of the cats.
It appears to happen after runniong at speed and then dropping to idle speed such as getting stuck in bumper to bumper traffic or exiting the highway and stopping at red light at the end of the exit ramp.
I am planning to get a tune...Will that stop the CEL and codes?
3 times in the past week the check engine light has gone on and the codes are P04020, P04030
They speak of inefficency of the cats.
It appears to happen after runniong at speed and then dropping to idle speed such as getting stuck in bumper to bumper traffic or exiting the highway and stopping at red light at the end of the exit ramp.
I am planning to get a tune...Will that stop the CEL and codes?
Burning Brakes
Joined: Jul 2000
Posts: 1,134
Likes: 1
From: Arlington Texas
I installed American Racing headers with high flow cats.
3 times in the past week the check engine light has gone on and the codes are P04020, P04030
They speak of inefficency of the cats.
It appears to happen after runniong at speed and then dropping to idle speed such as getting stuck in bumper to bumper traffic or exiting the highway and stopping at red light at the end of the exit ramp.
I am planning to get a tune...Will that stop the CEL and codes?
3 times in the past week the check engine light has gone on and the codes are P04020, P04030
They speak of inefficency of the cats.
It appears to happen after runniong at speed and then dropping to idle speed such as getting stuck in bumper to bumper traffic or exiting the highway and stopping at red light at the end of the exit ramp.
I am planning to get a tune...Will that stop the CEL and codes?
Burning Brakes
Joined: Jul 2000
Posts: 1,134
Likes: 1
From: Arlington Texas
I have a very extensive write-up on these codes if you want it.
Pro
Joined: Sep 2005
Posts: 595
Likes: 0
From: Palmdale CA
Thanks for the info. I don't know how this affects the cats, but when I had my free flowing catback on (BULLETS) I had no codes. As soon as I changed to a very restrictive catback (route66) I started getting these codes. Any relation??
The rear oxygen sensors measure the conversion efficiency or condition of the cat. High flow cats do not convert at the same rate as stock cats do and the algorithm in the PCM to measure this is based on an acceptable range from the EPA. Looking at the rear oxygen sensor activity in a scanner will show if the 'wave form' is correct. Properly functioning cats will produce a wave form at the rear oxygen sensors opposite of the front oxygen sensors. If the wave forms are similar, front and rear, than the rear sensors detect that the cats are not converting at an acceptable level and it throws a p0420 and/or p0430.
I have a very extensive write-up on these codes if you want it.
I have a very extensive write-up on these codes if you want it.
Burning Brakes
Joined: Jul 2000
Posts: 1,134
Likes: 1
From: Arlington Texas
I don't know how the catback would affect this code since the rear oxygen sensor is so far up. I've got Borla 2-tip Stingers that I don't THINK they are restrictive and got the codes before I changed the error mode.
