BBATCAR

iTrader: (1)

Hi All - I just had Heads only installed in my car (ported LS6 heads stage2.5). Car only has 61K miles and has lid, muffler and heads only, stock cam and everything else factory down to the manifolds.

SES light with P0430 code came on, "passanger side cat is bad", according to the code. I drove it about 100 miles before the light came on and if had 2 of the same code in the PCM. It installer swears it is not the heads but a bad cat and it is just a coincidence. He has done many LS1 heads only motors.

He cleared the code and drove it 30 miles no light so far but no WOT while I drove it because he stated the WOT could throw the code.

Could the heads effect the cat or codes? I plan on replacing the cat because I MUST pass emissions here and why I only went heads only.
Any feedback is appreciated.
Thanks.

UPDATE: I just thought I would post the findings on this in case anyone else has this issue. Spoke to a tuner and he said is was most likely the cat with a heads only install. $500 later, I had the cat replaced with a Magnaflow Direct Fit unit and cleared the codes. Drove 200 miles now, WOT, street and highway to 100 mph and no more SES light. Seems to be running great. I guess GM did a good job with the SES codes and PCM is accurate.

BBATCAR

iTrader: (1)

Bump

miker2

iTrader: (1)

an exhaust leak (missing gasket )will give you that code.

man-o-war

If he dropped the cat pipe while installing its possible that honeycomb partially collapsed and is blocking flow throwing the code?

BBATCAR

iTrader: (1)

Thanks for the responses. So it really could not be just doing the heads? So it may be they damaged the cat. All new gaskets are on the car so I don't believe it is a leak.

I was really more worried that I did the heads and that is causing cats to "melt".
Any other opinions? As soon as I have the funds, I'll do the cat. Just wanted to get a feel if it was the heads causing the issue.

salemetro

iTrader: (5)

Before throwing money at a new cat, install a wideband (either permanent, or temporary) into the exhaust. It's possible that the car is going pig-rich under PE/WOT which could trigger a P0430 code....as could a bad or dying rear o2 sensor. Was the car tuned after the head install?

danieloneil01

Doubtful as most mechanics don't.



OP, get your **** tuned and your tuner can turn off the SES light for the rear O2 sensors.

BBATCAR

iTrader: (1)

My plan is to get the car tuned, that will take care of the Lean/Rich issue if it really is happening. The tuner told me I need to take care of the cat and code issue first otherwise the tune is useless since he needs the emissions/O2 sensors to do there job.

The mechanic I used has tons of LS1 cars in the shop from sand rails to classic cars with LS1 motors in them. He swears with heads only (no cam upgrade), the car PCM would compensate. That is the reason I went heads only so I stay emissions compliant and the PCM is stock to pass emissions. I know a good tuner can fix that but the car has to be operating correctly.

I'm starting to regret the heads only mod if this doesn't get resolved so I'm reaching out on next steps. Got to fix the code/cat issue, then I will get a tune.

thechef

iTrader: (13)

drive the car some more and see if it throws the code again and go from there before going spending money

man-o-war

Good luckk buddy post solution here

BBATCAR

iTrader: (1)

Some very good points here - Thanks all. I think I will drive the car some more. Drove another 10 miles no issue but have not tried WOT.
I think I better check air/fuel ratio with a tuner first. A new cat is $450, I could spend that on a tune.

danieloneil01

During closed loop, yes, the car will use the pre-cat narrowbands to adjust fueling. If you go into PE or OL mode at all then all bets are off.

You can try this. Get car scanned and get print out from Auto Zone to determine which O2 sensor is giving the error and have them clear it before disconnecting. Swap the sensors around and go through the necessary drive cycles. If the code comes back then this will tell you if it's the sensor or cat that is bad without spending any money.

BBATCAR

iTrader: (1)

Pardon my ignorance, what is PE or OL mode? Will a tuner be able to check the fuel adjustment or those modes?

Unfortunately, I'm an older guy not too mechanically inclined, but will try your advice.