2005 5AT G35 Coupe 27K miles

Crawford plenum, Z-Tube/popcharger, Grounding Gear ground kit, UR pulleys, DC headers, Crawford cats, JIC Y-Pipe, Fuji exhaust, AAM ECU Re-flash, Turbo XS U-Tech. car has been tuned by AAM and has been running with no issues whatsoever for over a year.

car has been sitting for a couple weeks and battery was dead. jumped this weekend with no issues. drove the car both Sat. and Sun for about 30 miles each day. drove the car easy, not too hard, but did some higher speed runs. again no issues. have new Optima Red Top on order as I have had trouble with OEM battery discharging this winter after car sits for a week.

drove car to work today and service engine soon light came on...emissions problem? drove right to dealer to get scanned. code PO420...cat failure. dealer said both banks 1 & 2 are running rich. they wanted to adjust the idle air volume learner and then possibly an ECU re-flash to see if cats were bad. I suggested they don't do anything since car has been re-flashed and has the U-Tech. called tuning shop, but they have not gotten back to me. a mechanic friend of mine suggested changing the battery and then see what happens.

find it hard to believe the cats are bad since they are not that old.

any suggestions of what to look for before I call AAM back?

thanks in advance.

 

any ideas? anyone? just looking for things it might be that caused this.

my friend is thinking it could be a low voltage problem caused by the battery going bad and should change battery and clear codes to see what happens.

need new drive belts anyway so will take to AAM for service.

 

Once you reflash oem software all bets are off. Leaning mixture will increase cat temperature.
Aftermarket high flow cats have a very short useful life since by design the area of catalyst is small [more open space in honeycomb] to reduce backpressure.
Oem cats are warrantied to last 80k most aftermarkets only 12k.

"DC headers, Crawford cats, JIC Y-Pipe,............."

 

what would you suggest as the next course of action?

I am planning on changing battery first, then resetting codes and see what happens from there. if they trip the codes again, then we know it is not a low voltage problem and could possibly be the cats. the cats have 50K on them so they could be shot.

appreciate your quick response and advice as you are familiar with both sides, OEM and aftermarket. thank you very much.

 

for some reason the CEL just went away this weekend and I have done nothing to the car. could it just have been a problem due the car not being driven much over the winter? anyone have any ideas?

 

anyone?

 

idk, is ur car sounding or acting different...my car is vortech charged i have berk high flows and all of a sudden my car sounds different..like quiet and just different after doing some high speed runs...didn't drive it far after so i don't know if its down on power, just doesnt sound the same...no cel on the way home though..

 

no issues with the way the car was running at all. CEL just came on one day while driving car hard after it had been sitting for a while. CEL light went out on it's own after about 3-5 key cycles. think it was a low voltage problem with the OEM battery, which was really weak. changed battery to Optima Red Top, cleared the codes and no issues since. I'm happy since I was not looking to replace my Crawford HFC's. have about 50K miles on the Crawford's between two G's and have passed emissions with these...love them.

 

That's the rub the oem software is designed to check oem cats not aftermarket cats, so ecu can still show ok when a REAL EMISSION DYNO [measured emission] might fail.
That's why it is a Clean Air Act Felony to swap out oem cats and to present a modified car for emission as you could be defrauding the emission station into passing car.
Why many stations conduct a visual under car inspection.