[12ecofamilycar]

Hi, I use Torque Pro w obd2 adaptor to monitor stuff. My 1.4 cat temps range from 900s to high 1500s and are constantly changing depending on the driving condition. I've been using TP for at least 2 years.
I searched and this article seems to explain in techy terms:

Oxygen Sensor: Catalyst Efficiency

The catalyst efficiency monitor verifies that the catalytic converter is operating at a high enough efficiency rating to keep exhaust emissions within predetermined values. The PCM compares the signals from the upstream and downstream oxygen sensors to determine the state of the converter. These...

www.underhoodservice.com

 

[12ecofamilycar]

I'm just a diy hacker but...
A big culprit is a too rich fuel/air mixture which can be caused by a number of engine issues. The excess fuel doesn't get ignited in the cylinder and is passed through the exhaust into the cat which burns it off to try to make the exhaust emissions happy. Raw fuel in the cat will make it run very hot, (glow)

A couple basic "bandaids" for starters to help the possible fuel/air issue;

1. Use "Top Tier" gas whenever possible. ie. Shell, Mobil, Citco, Costco, Sunoco etc. They have superior detergent formulas to help your fuel system stay healthy. You can find a station near you here- TOP TIER - High-quality Fuel Performance Standard - TOP TIER™

2. Use a bottle of 'Gumout Regane' in the gas tank at a fill-up. $10.00. It will start cleaning your injectors and valves. It will not harm anything. There are many additives but I have had good experience with this one.

3. Try using a higher octane gas during hot summer driving. 89,91, or 93. Lots of debate on this but I have had success using it with both our Cruzes. It is more money but I think worthwhile for 2 months out of the year. It is mostly small displacement turbo engines (like ours) that will benefit the most.

4. As stated many times by super smart forum members-" catalytic converters do not fail on their own, it is an engine malfunction that causes p0420 and finally causes the cat to fall "below efficiency threshold".
But also- if you repair the engine issues, the catalytic converter can improve and move back within the acceptable threshold range.

5. I see you tried to find a recommended independent mechanic but is your dealer known for really good diagnosis skills? They may just have you buy a very expensive cat without finding the issue. Mechanic should look upstream of the cat. Evap, injectors, pcv system, AIR LEAKS! may cause the ecu to add additional fuel to make up for too much air leaking INTO the intake etc.
Check that the turbo waste gate is not getting stuck open or closed. A stuck closed waste gate is not good and I'm pretty sure can cause heat buildup.

Keep reading and searching the 10 years of Cruze Talk repair history even if you may not diy. You'll be better prepared to speak with the mechanic. Say hi in the new member thread.
Good Luck!

 

[12ecofamilycar]

Thanks for sharing your thoughts, car had been inspected for all engine related issues like lean, rich, misfire etc after installing new cat nothing find out neither by independent shop nor by dealer and also never had check engine light. That is why confuse about this situation.

"A little background my old cat(99k done) brunt down without any warning on a 5 hr drive, that was glowing red in night before failing. I tried to find out the root cause, took car to multiple mechanics as well but no success(no check engine light other then p420 before cat got burnt)."

Seeing that the original cat failed in a big hot way... only 3-4k miles ago, it would be good to be on the lookout for unusual engine stuff. There was a reason why that happened. Something intermittent that could come back. Was the cat that burnt an aftermarket cat, or the original GM?