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Chevy Forum: Pesky P0420 Code On 2006 Chevrolet Malibu
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Old 03-20-2016, 01:25 PM
MalibuTrouble MalibuTrouble is offline
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Default Pesky P0420 Code On 2006 Chevrolet Malibu

Within the past year, I purchased a 2006 Malibu off of a small town used car dealer. I had taken it for a test run and inspected it myself. I'm not an expert mechanic, the only time I can fix a car is if there is a how-to video on the problem and after I fix it once, Ill be able to do it for the rest of my life. Learning little by little I guess. The car was in good shape with a few small easy tweaks. It ran perfect with no problems at all for the first 3-7 days and then I noticed the check engine light was on. I had it taken to a certified mechanic who inspected it and said the check engine light was on because the crankshaft oil seal, and oil sending unit were busted up on it, as well as a crack in the muffler, but said that there was no need to rush to fix it as it wasn't hurting the car as long as I kept oil in it. They also noticed that the P0420 code was being thrown off and told me the catalytic converter needed a more in depth inspection to find out if it needed to be replaced. But, again, as long as the car wasn't giving me any problems, there was no need to hurry into fixing anything. Later on, I had saved up some money to get the oil leaks fixed and took it back to the same mechanic who fixed the oil sending unit and noticed that the timing cover was also busted on it. I had both the oil sending unit and timing cover fixed that day. I brought it home and it ran like a dream but, the check engine light was still on. The car had ran for months with the check engine light glowing as I was saving to have the catalytic converter checked on. On my way to work one night, I noticed the car would try to stall out on me while I was slowing down or coming to a stop until I hit the accelerator. It would run just fine as long as my foot was on the gas or the car was rolling. That went on for about a week or two and the the car just wouldn't run anymore. I could start it up but, it would not make it to the end of my driveway before it gave out. I let it sit until I could get it back to the mechanic who has been working on it. I hooked a small diagnostics reader to it and it threw off the P0420 code again. I finally got it back to the mechanic, explained what was going on with it, and they called me to inform me that most of the sensors, the throttle body, intake, and exhaust manifold was covered in oil blow by as well as very little to no oil in the car, and the right front wheel bearing had some wear in it. I had it all fixed. When I went to get the car, I asked them if the P0420 code was gone, they told me all codes were gone but that they reset the throttle body and that it was not uncommon for the codes to come back when the car's systems cycled back through. Not really knowing what blow by then was, I had asked them if that problem was fixed and what the chances were that it could happen again and what I could do to prevent it for reoccurring, they assured me that that problem was fixed as well. They had the car for almost an entire day. I've been driving the car for a little over a week now since its come out of the shop, making sure to check the oil levels in it before and after I drive it everytime. As well as keeping an eye on the check engine light. This morning, I had noticed the car was a little low on oil, a quart low. I put about a quarter of a quart in it, give or take, just to get it to a comfortable level to get it home as I was out of town. I drove it home, no problems. Later, on my way home from the store, I looked down and seen the check engine light was on again. I got it home, hooked the diagnostics handheld to it and it read out P0420. Currently, the oil level is fine. Under the car, near the exhaust manifold, I noticed a rattle...Almost like a bumblebee. Exact sound. I look under it and notice that the front of the catalytic converter, nearest to the engine is putting off a good bit of heat. Like looking at the road on a hot summers day, mirage-ish but, it isn't like that on the back of the converter, nearest to the muffler.

My biggest fear is that the catalytic converter is bad on it. With a little over $1100 already in the car on maintenance and repair and having no money at all, my question is, is there a way to tell if the catalytic converter is for sure the problem without having it taken off? The mechanic told me that if the code came back to have it brought back in and they will diagnose it again to find the problem but, they are closed today and open again in the morning. It'll be a tight squeeze or no chance of seeing the car at all due to it being early in the week. Ill need the car for the remainder of the week but, I'm afraid it might shut down completely on me again. I'm doing the best I can to not drive the car until I can get it looked at. When they told me the catalytic converter needed further inspection they told me that it could possibly be replaced with a straight pipe or flex pipe which would be the cheapest option because putting a whole new exhaust manifold and catalytic converter on it would run close to $1000.

Is there a way I can test the catalytic converter without taking it off? Could it be something else? Is it true that a flex pipe or straight pipe is equivalent to a catalytic converter? How does that work? Is it better to replace it entirely or have a pipe put on it? Any videos or sites to educate me on diagnosing this problem myself?

Any and all help is very appreciated!
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Old 03-21-2016, 09:02 AM
zora zora is offline
Join Date: Apr 2012
Posts: 3,322
Default Re: Pesky P0420 Code On 2006 Chevrolet Malibu

Is this mechanic the only "reliable" one in town? Seems to me he has never really fixed anything completely. Not sure how the crankshaft seal and oil pressure sending unit would cause a check engine light to come on, would love to know what code he claims they caused. Next everything is covered with oil but no explanation why, where is the oil coming from? Where is the leak, if he blames it on blowby why hasnt he done a compression test? Did he check the rear O2 sensor for the P0420 code? How is he going to get the check engine light to stay off with a straight pipe, the PCM needs a signal from the sensors to stay off. Get a second opinion from a different mechanic that other people use and trust.
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Old 04-07-2016, 08:12 AM
psmith32 psmith32 is offline
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Join Date: Apr 2016
Posts: 3
Default Re: Pesky P0420 Code On 2006 Chevrolet Malibu

A little late but
I was taught to check the temp. before the converter, then after.
if after its LOWER after converter is plugged/bad. Or going bad.
There are cleaners on the market, but they never worked for me.
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