Well I am now getting a check engline light after installing my 200 Cell Primary Cats, 2nd Cat Bypass and Fabspeed Exhaust system. I only have the Evoms Intake.

Before installing the full exhaust system I had no issues. After I installed it and drive maybe 5-10 miles it throws the CEL. I can reset the light and then it will randomly come back on again after 5-10 miles of driving.

The codes it throwing below are the following based on my Durametric. I know the cats are supposed to be CEL code free. It is a 2005 with 67k miles. Is it normal and possible that my o2 is failing?


P0421
Catalyst System Efficiency Below Threshold Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is currently active and causing a DTC light


P0431
Catalyst System Efficiency Below Threshold Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is currently active and causing a DTC light


P0299
Turbo/Super Charger Underboost - Value below lower limit value, test conditions are not-completed, fault is not currently active and is not causing a DTC light

 

Well I think I just figured out my underboost problem. My driver side diverter valve had a hose that came off. It was the smallest hose of the 3. Interested to see if that small hose could cause a CEL.

 

Well CEL came back on. This time only the codes for the o2 sensors. I guess the small hose on the diverter valve thru the CEL

 

Sounds to me like you need oxygen sensor extenders since the 200 cell cats are flowing much more exhaust than the stock cats. Did you install any?

Also, like you said, the P0299 code is unrelated to primary DP swap.

 

no i did not. what do they do? i thought maybe the o2 was just fouling.

 

No, your O2 sensor is most likely fine - dont you think it is odd that both of these O2 error messages showed up at the same time? These are misleading error messages since you just swapped out the downpipes. In lamens terms, your vehicles does not "know" you swapped out to higher flowing primary cats. The rear oxygen sensors measure how much exhaust gases are being passed through the main primaries. If the amount of gases passes a certain threshold, then the vehicle ECU assumes (based on stock setup) that either the O2 sensors are bad or the primary cats are bad. In reality, you put on higher flowing cats, so you are going to have higher amounts of exhaust gas reaching the O2 sensors, thus triggering the codes. The O2 extenders pull the top of the O2 sensor out of the exhaust stream just enough to reduce the exhaust reading to the ECU. So you are essentially, tricking the computer to keep it in its happy value range and keeping the check engine light off.

If you need a link to a O2 extender that will work for your application, shoot me a PM.

 

Wouldn't this lead to the car running lean? Cause now by tricking the system your air fuel ratio would be incorrect right?

 

No, you have two pair of O2 sensors per side - 4 total. The ones that affect AFR ratio are before cats (do not touch those). The ones that read the efficiency of the cats are placed after the cats (downstream). The second pair of O2 sensors ONLY measure the efficiency of the cats - no AFR at all.

 

Got it!! Thx for the info.

So the codes above I'm throwing is for the ones after the cat on each side then?

 

No worries.

Yep.

 

yea ditto on this..throw the extenders on the 2nd o2 sensors on each side and those CELs should clear and stay clear. I have never thrown an o2 CEL...and I run NO cats . Good luck.