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2001 Buick Cat/o2 sensor contamination P0420


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terasys
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May 16, 2012, 6:49 PM

Post #1 of 19 (5102 views)
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2001 Buick Cat/o2 sensor contamination P0420 Sign In

Well. My car:

2001 Buick LeSabre Custom 3.8 160k miles

has the infamous p0420 code. I have noticed decreased fuel efficiency (on average the last week its around 12 mpg.... yeah..)

I know the code points to the Cat not working efficiently or as it should, but I wanted to test the upstream o2 sensor first because that could explain the bad gas mileage.

It passed inspection last year only because the mechanic cleared the code and then let it slide. I decided to test the upstream o2 sensor first before shelling out 100's.

It seemed to be working fine: went up to 0.9 volts under high temps and went back down to under 0.1 volts very quickly in around 1-2 seconds. Seems pretty normal. BUT, the head of the o2 sensor was chalky white. Which is a tell tale sign of silicone contamination. I suppose this could lead to my cat being inefficient and thusly throwing the code.

The problem is: I read online that coolant has silicone in it. Last year I got a coolant flush and got it filled up. Since then, my coolant reservoir has gone from about 1/3-1/2 full to pretty much empty right now. Does it usually just go away like that? Could it be leaking into the engine somehow? Could this be put on the mechanic's (Sears..psh) fault? Did they mess it up somehow and make a leak?

I also have a pretty good (bad) power steering leak. I need to put a new bottle in about every 2 weeks or so. I ALSO have a slight oil leak too. The guy who owned the car before me said it just burns up as it drips off. I need to add a quart of oil every 3-4 months MAYBE. I haven't since probably last summer and it needed 2 quarts when I recently did add some.

The bottom of my car has a pretty decent layer of black tar/oil coating everything. including almost all of the hoses near the front axle. My car will leak (which I believe is power steering fluid) 100% of the time. No matter if I let it sit for an hour or 2 seconds. it is constantly dripping.

Any ideas?

Should I test the downstream o2 sensor? (pain in the ass)

Thanks!


Hammer Time
Ultimate Carjunky / Moderator


May 16, 2012, 7:02 PM

Post #2 of 19 (5096 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Some of what you are saying has a little truth and most of it is out in left field.

Coolant doesn't contain silicone, some of it contains silicates but not Dexcool which is what you should have in there.

You have a bad Cat. The PO420 rarely indicates anything but a bad Cat because of the criteria it takes to set that code. The white on the 0/2 sensor doesn't mean anything bad and that's pretty normal. You're way off on how the 0/2 is supposed to operate also. I don't know where your coolant is going but you should be able to find out with some careful pressure testing. That particular engine has a known problem with intake manifold deterioration causing coolant to leak into a vacuum chamber under it. There is a TSB on that.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 16, 2012, 7:23 PM

Post #3 of 19 (5072 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Link deleted.................. is where I found the information about the o2 sensors colors.

I wanted to save so money so what I was going to do was buy a cat online (they run from (what i saw) around 90-300) and I know a mechanic who will install one for about 75 bucks.

will that clear the code? Should I get him to install new o2 sensors as well? Or should I just buy a new upstream? Because honestly I went through 4 gallons (16 dollars) of gas going about 45 miles.

What is a TSB? Can you link this?


(This post was edited by Hammer Time on May 16, 2012, 7:29 PM)


Hammer Time
Ultimate Carjunky / Moderator


May 16, 2012, 7:33 PM

Post #4 of 19 (5046 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

We don't allow links on the site but I will post an image of the TSB. They don't list your year but it's still possible. As I said, you need to pressure test.

I wouldn't even attempt to buy a converter online. Just go to a custom exhaust shop and they will install one for likely less money that you can even buy one. My shop gets $180 installed for a universal cat.

As far as the 0/2s, don't be too concerned with the color as much as how they operate. Sensor will deteriorate over time so changing them is never a bad idea. The upstream is the only one that has anything to do with fuel mixture. The downstream is a Cat monitor only.







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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on May 16, 2012, 7:35 PM)


terasys
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May 16, 2012, 7:42 PM

Post #5 of 19 (5038 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Okay awesome.

I figured it would be like 400-600 for something like that.

I will call a couple places and see what the prices look like.

Thanks for that pic but where do I find more information? Just googling?

And: I read many reviews online that a new cat sometimes does not clear the code. Any reason why it wouldn't in my case? (Your best guess obviously).
Thanks again!


Hammer Time
Ultimate Carjunky / Moderator


May 16, 2012, 7:47 PM

Post #6 of 19 (5034 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

I have seen that code dozens of times and only once did a new Cat not resolve it and in that case, the exhaust pipe had a crack in it just ahead of the cat and the oxygen was confusing the sensors.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 18, 2012, 6:53 PM

Post #7 of 19 (4968 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

How long will it take to have the code come back on after clearing it? Its been over 25 miles since I cleared it and it has not come back yet..


Hammer Time
Ultimate Carjunky / Moderator


May 18, 2012, 7:14 PM

Post #8 of 19 (4961 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

It takes a while because the computer has to see very specific criteria and it may have to see it more than once.

Here's some reading for you on that code



CIRCUIT DESCRIPTION
In order to control emissions of Hydrocarbons (HC) , Carbon Monoxide (CO) , and Oxides Of Nitrogen (NOx) , a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The converter also has the ability to store excess oxygen and release the stored oxygen to promote these reactions. This Oxygen Storage Capacity (OSC) is a measurement of the catalyst's ability to control emissions. The Powertrain Control Module (PCM) monitors this process using a Heated Oxygen Sensor (HO2S) located in the exhaust stream past the 3-way converter. When the catalyst is functioning properly, the HO2S 2 is slow to respond to a large change in the HO2S 1 signal. When the HO2S 2 responds quickly to a large change in the HO2S 1 signal, the OSC and efficiency of the catalyst is considered to be bad and the MIL will be illuminated if subsequent tests also indicate a failure.

CONDITIONS FOR RUNNING THE DTC
  • Meet he conditions for engine warm up. Use the scan tool catalyst data list in order to verify the following.
  • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201-206, P0300, P0336, P0341, P0401, P0403, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449, P0502, P0503, P0506, P0507, P1133, P1134, P1336, P1351, P1352, P1361, P1374, or P1441 are not set.
  • The engine has been running more than 10 minutes.
  • The Engine Coolant Temperature (ECT) is above 70°C(158°F) and below 124°C (255°F).
  • The Barometric Pressure (BARO) is above 75 kPa.
  • The vehicle is in Closed Loop.
  • The Intake Air Temperature (IAT) is above - 20°C (-4°F) and less than 100°C (212°F).
  • The battery voltage above 10.7 volts
  • Warm up the catalyst.
  • Fully open the hood.
  • Place the transmission in park (automatic) or neutral (manual).
  • Set the parking brake.
  • Press and hold the service brake.
  • Each time the engine is started, the diagnostic can run up to 18 times. After the 10-minute run time and before the diagnostic runs the first time, the engine must run an additional 5 minutes between 1500-2500 RPM.

For any additional tests on the same key cycle, the engine speed must be between 1500-2500 RPM for 1 minute.
  • In order to activate the diagnostic return the vehicle to idle and put the vehicle in drive, or depress the clutch for a manual transmission.
  • Test the catalyst.
  • Place the transmission in drive (automatic) or neutral (for manuals with clutch depress).
  • VIN K California Emissions- Within 60 seconds the air fuel ratio will go rich below 14.1 for up to 6 seconds , then it may go lean above 15.3 for up to 8 seconds.
  • VIN K FED Emissions-Within 60 seconds the air fuel ratio will go lean above 15.3 for up to 6 seconds , then may go rich below 14.1 for up to 7 seconds.
  • VIN 1-With in 60 seconds the air fuel ratio will go rich below 14.1 for up to 7 seconds , then it may go lean above 15.3 for up to 9 seconds.
  • Check if DTC P0420 has passed or failed this key cycle using the scan tool.

CONDITIONS FOR SETTING THE DTC
The PCM determines that the catalyst's oxygen storage capacity is below an acceptable threshold.

ACTION TAKEN WHEN THE DTC SETS
  • The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
  • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC "Last Test Failed" clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
Check for the following conditions:
  • The PCM will not enable the catalyst test until following conditions are met:
  • The engine speed is plus or minus 100 RPM from the desired idle.
  • The Throttle Position (TP) is 0.0 percent.
  • The short term integrator is between -20 percent and +20 percent.
  • The catalyst test will abort if the vehicle falls outside the conditions listed below while the test is running:
  • The engine speed is plus or minus 125 RPM from desired idle.
  • The Throttle Position (TP) is 0.0 percent.
  • Short term integrator is between -20 percent and +20 percent.
  • The catalyst test may abort due to a change in engine load, for example, from the A/C or from the coolant fan. If this condition occurs, use the scan tool in order to force the cooling fans ON, and return to Step 2 in the table.

IMPORTANT: When using the scan tool to force the cooling fans on use the next list and previous list soft keys to enter the catalyst data list. If the catalyst data list is not entered this way the cooling fan control will be canceled.

  • More than 6 tests may have to be attempted in order to get 6 completed tests. An aborted test counts as an attempted test. The number of attempt tests is limited to 18 per key cycle.

After returning to an idle the HO2S 1 signal may stay rich or lean for several seconds causing the test to be delayed.
  • A faulty connection at PCM-Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Use a corresponding mating terminal to test for correct terminal tension.
  • A damaged harness-Inspect the wiring harness for damage. If the harness appears to be OK, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.





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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 19, 2012, 12:06 AM

Post #9 of 19 (4949 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Oh.. I see.

It came on tonight actually. After driving a total of 30 miles. but I didn't know it had to be specific criteria like that.

Thanks anyway. I got an appointment on 5/30 as supposedly the best auto place in the area. His appointments can take up to 2 weeks because so many people go to his place. Supposedly he also does not charge much.

Hopefully it works out okay


Hammer Time
Ultimate Carjunky / Moderator


May 19, 2012, 6:08 AM

Post #10 of 19 (4944 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

You're not looking for the best repair shop in town. You're looking for an exhaust specialty shop. General repair shops are not equipped for custom exhaust and will be more expensive.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 20, 2012, 1:01 AM

Post #11 of 19 (4923 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Well the thing is i Have multiple issues. I want all the leaks fixed as well. I have an appointment on the 30th to get it checked out. If getting a new cat installed is around 200-250 ill get it done. If i can find a better place in the area, ill do it there.

I havent seemed to find a custom exhaust place.


terasys
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May 20, 2012, 1:05 AM

Post #12 of 19 (4922 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

The closest thing to an exhaust shop near me is Monro.

Are they okay?

I believe I have heard mixed things about them.

Edit: On their website they are offering a 30% off muffler/catalytic converter sale.

Will that be pretty cheap? I will call tomorrow.

Thanks again


(This post was edited by terasys on May 20, 2012, 1:07 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator


May 20, 2012, 4:51 AM

Post #13 of 19 (4919 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

I have no specific problem with any chain. If they are having a sale go for it. Best will always be OE stuff for exhaust items IMO but if it works and a bargain can't argue,

T
(sorry for spammer being removed now)
_________________________________________
Long retired now


Hammer Time
Ultimate Carjunky / Moderator


May 20, 2012, 7:55 AM

Post #14 of 19 (4912 views)
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It doesn't matter who they are as long as they have a pipe bender on-site. That would mean that they are in the business of making custom exhaust and have the toola and ability to do what's needed at a reasonable price. If they do not make custom exhaust on a regular basis, they cannot be competitive with the price. Midas may be the exception to that. They are always kinda expensive.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 20, 2012, 2:32 PM

Post #15 of 19 (4896 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Well.. I called one Monro and they said they cannot give me an estimate so I made an appointment on Tuesday morning for them to check it out.

So I called another Monro and he calculated the cost to be 465 for a universal and 700 for an OEM.

yeah.... I will keep looking. That is ridiculous

Edit: Should I be looking for custom exhaust shops?


(This post was edited by terasys on May 20, 2012, 2:33 PM)


Hammer Time
Ultimate Carjunky / Moderator


May 20, 2012, 2:35 PM

Post #16 of 19 (4892 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In


Quote
Edit: Should I be looking for custom exhaust shops?


Didn't I say that 3 times?




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 20, 2012, 2:38 PM

Post #17 of 19 (4888 views)
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You said "exhaust specialty" shops.

I have no idea if that is the same as custom? How does custom which includes like stainless steel compare to just having exhaust as a specialty? I guess it is clearer to trained eyes..


Hammer Time
Ultimate Carjunky / Moderator


May 20, 2012, 2:43 PM

Post #18 of 19 (4881 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

OH, come on............


Exhaust specialty...................... to mean specialize in exhaust repair.



Maybe you recall reading this....


Quote
Just go to a custom exhaust shop and they will install one for likely less money that you can even buy one. My shop gets $180 installed for a universal cat.





~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



terasys
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May 20, 2012, 2:45 PM

Post #19 of 19 (4875 views)
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Re: 2001 Buick Cat/o2 sensor contamination P0420 [In reply to] Sign In

Hahaha Okay okay okay. I got it. I got a couple places lined up.




2001 Buick Cat/o2 sensor contamination P0420


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