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2012 Chevy equinox 2.4L at about 135K miles threw a fan belt about 6 months ago on a road trip. Limped it to a dealership for fanbelt replacement and they said the timing chain was making a lot of noise and need replaced too. So I got it back home and had a shop do the timing chain with new tensioners and guide vanes as well as new water pump. A few days later I noticed the P0420 light on, but the shop who did the timing chain said I had a cracked exhaust manifold and likely a clogged catalytic converter due to rich running engine due to timing issues. So I replaced the exhaust manifold (which was badly cracked) and the Cat as well as both upstream and downstream O2 sensors. So after a decently long road trip we get back, and my wife takes the car around the corner to the store and here comes the check engine light and I check and its still the P0420 code.

Anyone know what is going on here? Did these guys not get my timing right? Are the O2 sensors brand sensitive? Mine are Walker brand from Rock Auto.

Thanks for any advice
 

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Anyone know what is going on here? Did these guys not get my timing right? Are the O2 sensors brand sensitive? Mine are Walker brand from Rock Auto.

Thanks for any advice
Yes it is possible when installing timing chains to get one a tooth off.
However I would not go there first.

There have been several posts on this forum where owners have had problems with aftermarket sensors.
I would start with changing to AC/Delco O2 sensors.
 

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2012 Chevy equinox 2.4L at about 135K miles threw a fan belt about 6 months ago on a road trip. Limped it to a dealership for fanbelt replacement and they said the timing chain was making a lot of noise and need replaced too. So I got it back home and had a shop do the timing chain with new tensioners and guide vanes as well as new water pump. A few days later I noticed the P0420 light on, but the shop who did the timing chain said I had a cracked exhaust manifold and likely a clogged catalytic converter due to rich running engine due to timing issues. So I replaced the exhaust manifold (which was badly cracked) and the Cat as well as both upstream and downstream O2 sensors. So after a decently long road trip we get back, and my wife takes the car around the corner to the store and here comes the check engine light and I check and its still the P0420 code.

Anyone know what is going on here? Did these guys not get my timing right? Are the O2 sensors brand sensitive? Mine are Walker brand from Rock Auto.

Thanks for any advice
Was the CAT OEM or a universal unit welded in place? Would agree that some others had problems with certain types of sensors.

Make sure the wiring and connectors to the rear sensor is not contaminated with any oil or other debris. These sensors draw air from around the wiring and connectors for comparison to exhaust O2 levels, and if it is restricted or blocked, you will set P0420. Also check to see if it had the original oem connector, or one that had to be cut/spliced to your harness.

I recommend buying an UltraGauge MX to monitor many functions and sensors of the engine, including O2 voltages and temperature. Great investment, and it sits easily on your dash, no batteries, nearly plug-n-play. Costs $90. I was able to detect problems with my battery before it failed completely and recently discovered a vacuum leak. The unit can be configured for alarms long before the CEL comes on. Example the alternator over voltage will not trigger until it hits 17v. You can set an alarm before it reaches that critical point. Same for fuel trims, set a level below to detect a rich or lean conditions before it causes major problems, like in your case with the CAT.
 

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Is your vehicle a California emissions vehicle ? Label under the hood will determine that. If a NON California cat is put into a California vehicle it will erratically and constantly set the cat inefficiency code as PCM calibrations are different. My brother had a shop replace his cat in a Impala which was sold in NJ which is Cali. spec. state and it constantly set the same code every few days. They used a non C.A.R.B. cat. and not the C.A.R.B. compliant one. Cats are specific to the vehicles emissions certification.
 

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Discussion Starter #5
Hey thanks guys for all the help. I think my car is a California emissions car? See photo. If so what is a low cost option for a cat? I guess it has to be CARB compliant?
16920
 

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Cost will be left arm, plus 1st born male child. High end cost will be both arms plus male child. Cats are warranted for 8 years or so.
 

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Yea A cat problem for sure out here in California I'm shopping for one that's nice a lot of people say their car throws that same code after they install a new cat maybe the quality just isn't there. I got one that's poisoned from burning oil for 60k miles. The stock one looks pretty well built trying to find one just as good.
 

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Discussion Starter #8
Well I decided this is not my problem. I don’t live in California and have no intention of doing so. The cat I have on there is good enough. So I did the O2 sensor hack. For the 2012 equinox you need a 330K resistor and a 1uF electrolytic capacitors rated at around 50V. Resistor on line on the black wire and cap across the black and grey with positive side on resistor downstream of the sensor. There is schematics online just don’t use the resistor value in a Chevy it’s too high.
All good now my downstream O2 sensor is now graphing at nice slow pulse at .45V so ECU. And no this car isn’t burning oil.

16922
16923
is happy!
 

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Gotta love someone who understands electronics at the component level. 🙂
 

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One can also use a spacer that holds the downstream O2 sensor further out of the exhaust stream for an aftermarket cat that sets codes.
 
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