Engine and TPMS light- 2011 LLT V6

[Saltee]

Hello - I’m not sure where I should be posting questions so this maybe redundant.

My sons 2011 Lt 1 TPMS light and engine light are on. I have correct tire pressure and have “relearned” the system with no results. The car had been sitting for over a year prior to gifting it to him for holidays. I reset the ECM and the lights (TPMS and engine) were no longer present. The TPMS was relearned after the reset and all 4 tires read 32psi although the PSI is 35 all 4 tires. The engine light was steady - not blinking- since the purchase. Car runs well almost too well for a 16 year old. The only OBDII code I’ve ever received is P0420. I’ve replaced gas cap, changed oil, replaced coolant, air filter but not the plugs yet. The car had old gas and I’ve since been adding premium gas. I’ve read in the forums of a relearning process for the car by driving it @ 55mph for certain distance and time..etc. again the car is running great. The TPMS light came back on after approx 20 miles and the engine light soon followed.

I’m thinking that the TPM sensors need to be replaced- the sensor light blinks repeatedly after startup then stays solid. The engine light- I’ve read could be bad Cat - I’m doubting that and leaning toward the upstream O2 sensor.

I hope I was detailed enough in my breakdown. This is my first post. I appreciate your time and any/all advice. Thanks again!

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[Sir Nuke]

Welcome to our happy little corner of the net, and to Camaro5/6. There is a BIG fridge on the back porch with anything you can think of in it...help yourself...of course only take what you can LEGALLY have. Make yourself at home on one of the big fluffy couches, kick your shoes off, put your feet up on one of the tables, yes we are allowed to do that, mom's, wives', husbands, girlfriends and boyfriends here don't care....and take it easy.



oh...btw....every once in a while a food fight breaks out...so you may not want to wear nice clothes here.

Welcome!!

[AlanRubin]

Upstream sensors do not throw P0420, or P0430, those are your downstream
sensors. All they do is monitor the cats. They have no impact on air and
fuel mixtures. The P0420 means the primary cat is bad, or the sensor is
bad. These cars are very sensitive to flow rate. When the downstream sensor
readings match the upstream too many times, that is when the code is set.
It will not effect driveability of the car. When my secondary cat went, I got
the code, and those are not even monitored. I added spacers, and that took
care of that. Do not touch your upstream sensors, they have nothing do do
with P0420 or P0430 codes, those are downstream sensor codes.



TPMS, mine doesn't work right either. I can set all four of them, they all work for
15-23 miles, then all four go out, the light blinks, then goes solid. I stopped at a
sheetz, programmed them all again, ran 16 miles, and all four went out again. I
gave up on it.

[Saltee]

Thanks. I’m getting conflicting info on the P0420
Your issue with the TPMS is exactly what I am experiencing.
The P0420 code in a Chevy Camaro will often be thrown one of your oxygen sensors are not functioning properly. Typically, the code will be triggered by the upstream oxygen sensor (before the converter).

https://www.700r4transmissionhq.com/p0420-chevy-camaro/

[AlanRubin]

Upstream sensors DO NOT trigger P0420 codes. That link says, P0420 is often caused by
a bad O2 sensor. Mine is definitely cats. P0420: Catalyst System Efficiency Below
Threshold. That is exactly what it means, they're loosing their ability to function
properly. Your upstream sensors are the ones responsible for telling the ECU what fuel
and air ratios to use. The downstream ones, monitor what comes out of the primary
cats. The secondary cats are not monitored, but, if they were removed or
hollowed out, the flow rate changes, and those codes would also set. I know
that for a fact because I chopped mine off. I put spacers on the sensors, and
that fixed it.

The BAD sensor If it is bad, is going to be the passenger side, AFTER the
primary cat. This will also happen if you use a Bosch sensor, and not a
factory sensor, even if the cats are good. I had a P0430 code, that was
because there was a Bosch sensor in it. I replaced it with a factory sensor
and the code did not come back. Well, now I have both 20/30 because I
have NO cats since the just the no secondary cats.

I have never touched the upstream sensors.

[Saltee]

Replaced all TPMS and “relearned” them with tool. Received all of the correct horn chirps and individual lights coordinated. The tpms light is on and the PSI reads 0 (not - - as it did before replacing the TPMS) on all of the tires. Does my son just need to drive it?