fnbrowning

In May of 2005, I installed a Comp Cams cam & springs & a ported throttle body. In October of 2005, I started seeing SES codes for: P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) and P0420 Catalyst System Efficiency Below Threshold (Bank 1).

I went back to my tuner in Oct and had him delete the rear O2's.

In Jan of this year, I got SES Codes: P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) and P0420 Catalyst System Efficiency Below Threshold (Bank 1) again! I thought something might be weird with the front O2, so I replaced Bank 1 Sensor 1 with a Bosch O2 sensor and cleared the codes with AutoTap.

Now, I’m getting a SES AGAIN for P0420, Catalyst System Low Efficiency, Bank 1.

In October I’m sure I saw the tuner delete the code and save the bin to my PCM. So WTF is going on here? Is this P0420 indicative of something going awry somewhere else in the computer, or did the write to my PCM not ‘take’ for some strange reason?

Any ideas on what I can do to get rid of the problem for once and for all?

LoWeLL216

iTrader: (1)

If it's still thowing the code I'd imagine it either was deleted or not deleted properly. Are you still running cats? and has one gone bad? I'd address the code itself instead of just deleting it. Installing a cam and springs shouldn't make you throw those codes.

HumpinSS

iTrader: (1)

Sounds like it hasnt been deleted

SmokingWS6

iTrader: (1)

I agree on the not deleted. Whoever tuned it have them pull up code p0420 < no error reported < ses off, then reflash.

Zombie

iTrader: (2)

I've had an issue with tunercat and deleting that code before. I deleted the code but it was still present. What software was the tuner using?

fnbrowning

Tuner was using LS1edit, I think.

KillerWS6

P0420 usually means you have a bad cat. if you're still running cats, then change the bad one (I think the p0420 is the driver's side). If you have under 80K miles, your delaer should replace the cat for free. If you're not runnig cats, something else is hay-wire .

camarokid94

iTrader: (2)

there is a PCM update for false setting of p0420 codes. i had them in my car and im a tech at a chevy dealer so we put both cats in and new rear 02s in both like a week later it came back on. i found a reflash for it setting false p0420 and whatever the other bank code is p04(& and has never came on yet

fnbrowning

I should posted my mod list includes the Dynatech SuperMAXX Header System with the high flow cats. There is less ~6000 miles on the cats, {so they can't be clogged and if I didn't have the O2 codes deleted, I'd have O2 sims there, so there should be no input from that rear sensor!

Awww sh-t! Is that true? Reflashing the PCM would erase my tune. Then I'd have to pay to have it retuned, because if it was reflashed back to the stored performance tune, {after a factory 'update'} it would probably re-write the false setting back!

SmokingWS6

iTrader: (1)

Don't worry about updating the pcm, losing the tune ect. It was probably overlooked by accident while setting up the tune. Its a simple fix.

fnbrowning

I went to back to my first tuner today. He wanted $70.00 to fix what he forgot to program!

Needless to say, I won’t be dealing with him again. I called a local guy that uses tunercat software. He found the O2's were deleted, but the P0420 settings were not turned off. He pulled up code p0420 and set it to off, as SmokingWS6 suggested.

I’m driving a few hundred miles this weekend, so we’ll see if the SES stays off, but I can’t see why I’d ever throw a code P0420 again.

Makes me mad that the first guy did not use due diligence to program properly. Now, I’m beginning to question the entire tune. This spring, I just may have it done over, done right.

Thanks for everyone’s help!

mike s.

iTrader: (2)

I have found that when deleting rear 02's, sometimes you have to delete the low catalyst efficiency codes as well.

You have to delete these to start:
Bank1: 137,138, 140, 141, Bank2: 157, 158, 160, 161

Some cars will still throw these codes if left undeleted:
P0420- Low catalyst efficiency
P0430- Low catalyst efficiency B2

Its weird how one specifies a bank and one does not. I wonder if it was implied B1?

I left 420 & 430 on in my car, does not throw codes, but then I do not have cats.
My buddy's car would not stop throwing codes until they were deleted

Now 135 is usually a tell tale of a bad o2 sensor, 135 is B1 S1, so the only remedy is to replace it, deleting sensor one on either banks is not an option, they are needed for fuel trim adjustments by the PCM. Bosh replcements at the parts store are about $70, replace and clear the DTC.

horist

wow... that's utter BS ... that should have been removed when he disabled the other rear O2 codes....