Catalytic Converter Issue 2010 LaCrosse CXL

tomtella

Full Member
28
1
3
Wolcott, CT
Buick Ownership
2010 LaCrosse CXL AWD
About 4 months ago, at around 104,000 miles, my check engine light came on. It was P0402, Catalyst System Efficiency Below Threshold Bank 1.
I reset the light and it stayed off for about 400 miles, then returned. I went through several cycles of this and then tried replacing the O2 sensors, not believing that I had an actual catalytic converter failure. But the check engine light would faithfully keep coming back on about every 400 miles or so. Finally, I gave in and decided to replace the converter. Being Bank 1, the firewall-side converter, I decided to let the local Buick dealer do the job. It cost about $1300 but it fixed the problem. This was the only time my LaCrosse made me cry. This car is one of the best cars I've ever had.
 

dsinatore

New member
1
0
1
Buick Ownership
2010 Buick Lacrosse
About 4 months ago, at around 104,000 miles, my check engine light came on. It was P0402, Catalyst System Efficiency Below Threshold Bank 1.
I reset the light and it stayed off for about 400 miles, then returned. I went through several cycles of this and then tried replacing the O2 sensors, not believing that I had an actual catalytic converter failure. But the check engine light would faithfully keep coming back on about every 400 miles or so. Finally, I gave in and decided to replace the converter. Being Bank 1, the firewall-side converter, I decided to let the local Buick dealer do the job. It cost about $1300 but it fixed the problem. This was the only time my LaCrosse made me cry. This car is one of the best cars I've ever had.
Hello Tom,
Here we are 2 years later and i have the exact same problem with my 2010 Lacrosse.
Just this week at 105,000 miles, my check engine light came on with a P0402 Bank 1 error.
Do you think they made these cats to expire at 100K?
Thanks for the info, was wondering if I should replace the O2 sensors as well?

Dino
 
22
3
3
Buick Ownership
2011 Buick Lacrosse
I have I nought mine at 96k the first thing I did was change the spark plugs and transmission screen. I used NGK plugs. Instead of the OEM. I was mixing mid grade has with regular. And I have the same problem. I'm not sure if the gas makes it rum sluggish sometimes or not
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674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
Don't run higher octane on the NA 3800 motors,.. might fry the cat prematurely.
87 octane only,. Unless you have a tuner and bump up the timing a bunch.
 
22
3
3
Buick Ownership
2011 Buick Lacrosse
I was using 89 octane because I thought at first thats what I have to use but. I have stopped. Mine has a 3.6l. I used cataclean to see if that will work. I reset my check engine light about 300 miles ago at least but it has not came on since. I'm wondering if I should change the 02 sensors or not. Or could the problem be with the CAT.
 
674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
You can try a 02 bung extension. Some aftermarket 02 heaters are a bit sensitive... the extensiin makes the 02 sensor sit a inch or 2 farther away from the cat.
 
22
3
3
Buick Ownership
2011 Buick Lacrosse
I never even heard of a bung extension. I will see if the sluggish horse power continues.
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674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
I never even heard of a bung extension. I will see if the sluggish horse power continues.
If your engine seems to have lost power and doesn't rev up freely under acceleration along with a cat 02 code,. Chances are pretty good your cat is toast.
I've had bad 02 heater cat sensors on a couple different cars and performance didn't suffer.
 
22
3
3
Buick Ownership
2011 Buick Lacrosse
The sluggish was off and on. And I was switching back and forth between the different types of gas. SO your saying bad O2 sensors wouldn't make it run sluggish. Or are you saying a bad Catalytic Converter wouldn't make it run sluggish.
 
674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
The sluggish was off and on. And I was switching back and forth between the different types of gas. SO your saying bad O2 sensors wouldn't make it run sluggish. Or are you saying a bad Catalytic Converter wouldn't make it run sluggish.
Bad cat would make it run sluggish... Bad 02 sensor would not affect the power too much if any.
 

kevinande

Full Member
32
1
8
Buick Ownership
Buick
I have I nought mine at 96k the first thing I did was change the spark plugs and transmission screen. I used NGK plugs. Instead of the OEM. I was mixing mid grade has with regular. And I have the same problem. I'm not sure if the gas makes it rum sluggish sometimes or not
If the original owner(s) never changed the plugs that could be source of your issues. The catalyst should last the life of the vehicle, if you take care of the vehicle of course. That means changing the plugs at reasonable intervals. I change mine every 40,000 miles. Not saying you need to do that, but certainly not every 100,000 miles. The fuel octane rating will have nothing to do with how the vehicle is running unless you are purchasing low quality or contaminated fuel. The car is designed to run on 87 octane, however the car is smart enough to compensate for higher octane fuel just as it can adjust from gasoline to ethanol (assuming you vehicle is flex fuel). Octane ratings are simply a measure of how resistant to detonation a fuel is. Has nothing to do with power. High octane fuel will only negatively affect your wallet. If your catalyst is toast then it could be clogged or simply not up to spec. If it is partially clogged then you could have power issues. If the 02 sensor is bad it could possibly affect engine performance, however I would think the upstream sensor would be more suspect than the downstream if engine performance is a problem and the related code was an 02 sensor. I have no idea what this bung thing is, but I prefer OEM parts.
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22
3
3
Buick Ownership
2011 Buick Lacrosse
Thanks for the info. Its been running ok since i stopped using the higher octane. I Bought it with 96k miles and changed the spark plugs was the first thing that I did as well as transmission filter. I will keep you posted.
 

nlacomb

Buick Newbie
13
1
3
Buick Ownership
Buick
I have a 2010 CXL with the 3.0. I've replaced both front and back CATs twice each. My rear is throwing a code again, I'll have to replace it a third time here soon. I end up replacing them with off brand CATs for 150 bucks online. I refuse to pay the 800 they want for OEM. Oh, my Buick has 220,000 miles on her.
 
674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
I had a downpipe with a magnaflow cat and it never went bad.
Just because the 02 heater throws a code for the cat being bad doesn't always mean the cat is bad.
 
22
3
3
Buick Ownership
2011 Buick Lacrosse
My lacrosse has about 107,000 miles. I had no problems until a month after I had my spark plugs changed. I would get code P0420 I reset it and it wouldn't come on until about 600 miles later this happened twice. So in between the first and the last time i used cataclean to see if that would work. Like I said the light came on for code P0420 about 600 miles later. Now day before yesterday the code came on so i reset it. And today it came on with code P0420, P0430. Im wondering is it the Cat, 02 sensors, NGK spark plugs that were installed, Leak in the intake gasket when installing the spark plugs. Any suggestions???
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674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
My lacrosse has about 107,000 miles. I had no problems until a month after I had my spark plugs changed. I would get code P0420 I reset it and it wouldn't come on until about 600 miles later this happened twice. So in between the first and the last time i used cataclean to see if that would work. Like I said the light came on for code P0420 about 600 miles later. Now day before yesterday the code came on so i reset it. And today it came on with code P0420, P0430. Im wondering is it the Cat, 02 sensors, NGK spark plugs that were installed, Leak in the intake gasket when installing the spark plugs. Any suggestions???
Changing spark plugs would have nothing to do with the cat going bad. Maybe if the Gap was incorrect it might affect the cat a little, but probably not enough to cause any concern (but I could be wrong). Even tho most spark plugs are pre-gapped, some may not be and the ones that are could of been dropped or whatever. Checking the gap on the plugs before installation is very important.
 
674
145
43
S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
Yeah I think those were pre gapped. But would a leak in the intake gasket cause the same codes?
I'm not sure. But there is the possibility of coolant leaking into the chamber due to a lower intake gasket leak.
And coolant in the chamber would probably damage the cat or at least not allow it to work properly, thus setting off a code.
 
174
24
18
Buick Ownership
2016 LaCrosse
Makes me think (trouble begins). Nothing I know of that monitors the exhaust after the converter. There's the feed back from 02 level sensors but they're before and nothing beyond.

Back when I had my '84 Turbo Z I took the converter off and replaced with a straight through glasspack muffler. Acted like a resonator of coarse but no codes. Emissions still not tested in Androscoggin County and resembled converter at glance. Would I ever do it again, absolutely not.

Now on my 13 Boss the 02 sensor is directly before converter (called bricks on that), 2 of each. There could very possibly in that scnerio be some back pressure or residule converted exhaust that the sensor may also read at times, can't say for certain. Only thing beyond that are resonators and Corsa Xtremes (but would change mufflers lol), love those things. Photo: image.jpeg
 
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