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  #1  
Old 04-24-08, 06:59 PM
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Tell me what you think

96 Pontiac Sunfire GT 2 Door DOHC 2.4L
i have 2 codes that appear in the computer.

#1 P1601 PCM Serial Common ECM over temp ( computer is frying)
#2 P0420 Catalyst Efficiency Low bank1

my cat has been nocked out from previous owner, I beleave to make my Dual mini cherry bomb exhaust loud.

I would replace the computer but i do beleave they are $$$ there are always junk yards, but i am taking a big chance there.
I did replace the front O2 sensor to help the computer bec that one was shot. The back o2 sensor is probley going bad but those are like 70 because they are heated.

Tall me what you think about my problems
 
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  #2  
Old 04-24-08, 08:29 PM
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likely your back O2 sensor will not work correctly with out a cat, temp affects them a lot. I would think seriously about replacing the cat. if you want the noise don't run mufflers just the cat. Personaly I like a quiet car (less likely to attract unwanted attention) plus as I age I don't hear so well anyway (i can't hear crickets). I would think about the computer if it is bad or going bad you will need it to keep your milage up and car running properly.
Murphy was an optimist
 
  #3  
Old 04-25-08, 05:21 AM
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First off.....Have your PCM checked Proffessionally. I know the bucks are hard to swallow sometimes...But the parts stores that offer free code scans often Do not have the knowledge or experience to diagnose a "shoe - Lace", But they will be able to sell you one if their stock boy deems it necessary.

O2 sensors WILL NOT do anything for your CHeck engine light, or your codes.

You have O2 sensors before and after the catalyst. By design, they are responsible for reporting back to the PCM. When the PCM gets the same "Oxygen Content " reading from both sensors, the PCM decides That the CAT is not doing his job efficiently enough. In your case....Not at all , since it is "Hollowed" out. Your only choice in this case is Catalyst replacement.

DTC 1601........ To the best of my Knowledge.. 1600 series of codes refer to GM's "Immobilizer" anti theft sequence. Although PCM damage can occur from Malfunctioning outside sources, It is unlikely that the Pcm is damaged from this. More likely the Immobilizer system is not functioning, and the serial data doesnt exist.
I would replace the computer but i do beleave they are $$$ there are always junk yards, but i am taking a big chance there.
These PCM's are programmed for the specific vehicle that they are installed in,Complete with VIN number. Junkyard PCM's are often completely useless
 

Last edited by Unclediezel; 04-25-08 at 05:44 AM.
  #4  
Old 04-25-08, 11:55 AM
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i Go to an auto motive class at school. the teacher has been through college. I used a snap on scanner to check the codes.
yeah probley wont go to the junk yard then.. If you can find me a place in Ionia MI so i can price one, that would work. i don't think auto zone carry them for the computer
 
  #5  
Old 04-25-08, 01:31 PM
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YOU need to put your car back to factory specs with a working cat first...then and only then can YOU attempt to perform further diagnostics
 
  #6  
Old 04-25-08, 01:48 PM
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that part i will agree with Carguyinva.

and i work on large gas and diesel engine [ industrail size btw ] and master electrician also.

now let to the main point here many ECM do have program that will sense alot of the items and some area not working like cat converter is missing or malfunctioned it will programmed to run diffrent power setting [ useally derated or limp home mode one of the two ]

and get all the proper related parts on there then you can able scan the cuprit and go from there.

Merci,Marc
 
  #7  
Old 04-25-08, 05:25 PM
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i have really thought about Putting a new cat on but i dont want to lose the cool sound of my exhust (dual mini cherry bombs) this car has two, the cat then another much smaller one.

This car has 119,000 on it, very little rust

This car sounds like a sweet rice buner. i have nothing agunst foren cars, i love them
 
  #8  
Old 04-25-08, 07:04 PM
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Look into getting a O2 SIM. It basically tricks the computer into thinking your rear O2's are getting good readings. This is done alot for people who remove the cats.
 
  #9  
Old 04-25-08, 07:28 PM
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hmmm...and a blatant violation of the clean air act. which carries a hefty fine for DIYers and an even heftier fine for those of us that are expected to know better.
 
  #10  
Old 04-26-08, 02:58 AM
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Originally Posted by HotinOKC View Post
Look into getting a O2 SIM. It basically tricks the computer into thinking your rear O2's are getting good readings. This is done alot for people who remove the cats.
You should see how the owner reacts when the DMV/DOT inspectors catch them and when they do bust them they will not renew the vechile registeration until that is be done repaired propely and they will run thru the sniff tester [ basically a exhaust anysizer ] to make sure it pass

i have one county next to me they do inspect them very carefully with gas engines they check the whole 9 yards with diesel engine depending on age of the unit most useally take a snap test [ a quick rev up to check the exhaust smoke level ] but the area where i live my diesel unit is extempted from the inspection but myself i know it will not be extempted not for long due they are starting to crack down some owner really crank up the diesel engine in hard way.

oh by the way it don't matter if you used gas or diesel fuel any dyed fuel your butt will be busted min of $5,000 fine and up [ heard about 8~12 K range ].

Merci,Marc
 
  #11  
Old 04-26-08, 04:33 AM
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You should see how the owner reacts when the DMV/DOT inspectors catch them

Not only Vehicle owners......Ive seen my share of Techs in handcuffs, while the DOT inspector and State policeman fill out the paperwork. Ive heard every story in the book..."Oh , The cops dont bother us around here", or Everyone else has one, they wont target Me....
Fact is ...when the word comes down from the top dogs with the Gold stars, 7or 8 hundred of you will be Snatched up in a weekend....They will impound you vehicle, and very rarely do you get it back in the condition it was in when they took it...

I mentioned somewhere in another thread.......If you want your car to look , feel ,or sound "COOL" ...either get ready to make some compromises, or have plenty of Disposable cash.
Your in school for this trade......And you will soon realize that all the "Cool" in the world doesnt make up for the fact that it sits in the driveway, because it runs poorly and you cant stand to drive it.
 
  #12  
Old 04-26-08, 08:13 AM
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Whoops, I apologize for that. I forgot about the states that have vehicle inspections.....
 
  #13  
Old 04-26-08, 08:24 AM
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I have alot of thinking to do about this.

The O2 sim would be a posibility but i have read on that. drilling out a nonfouler spark plug then another is really not my thing.
I am going to try and see if i can borrow some more money, to get the cat. I don't want any more fines!!! or this car to be impounded!!!

I know the cat is not like a muffler because they are still loud going down the road after the muffler falls off. But do you guys think it would stilll sound good after a new cat is put on.
 
  #14  
Old 04-26-08, 10:33 AM
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Originally Posted by HotinOKC View Post
Whoops, I apologize for that. I forgot about the states that have vehicle inspections.....
the clean air act and its amendments are federal legislation and the penalties are pretty severe...as they should be. i don't live in an ozone non attainment area (no smog stickers or tailpipe tests) but there is at least one shop in this area that has been busted for "modifying" cats...what uncle diesel said above is right on...the position that "they won't catch me cuz i don't live where there is testing" doesn't matter...it's illegal to modify emission systems from the manufacturer's original configuration...in all 50 states.
 
  #15  
Old 04-28-08, 04:52 PM
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As i have looked underneath my car this is what noticed and don't under stand. You know how there is a triangle to connect the cat to the rest of the exhaust. It looks as if it has ether been mested with or in between the triangles (i do beleave there is supose to be a gasket there) has seperated. and around the corner of bolt of the triangle is missing. I also beleave my O2 sensor in the back is original i tried to turn it and did not buge

This is what i think ether the cat has been nocked out or it has failed or my 2nd O2 sensor is bad.

What i don't get is how do you get the honeycome out if you are trying to knock it out? From the ehaust mainifold pipe to the cat cut marks or sighs of welding other than the factory one. Do you start up the car and hope for the best?
 
  #16  
Old 04-28-08, 05:13 PM
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Take it out of the car and drive a crowbar thru it


Since Ive delved into my illegal tidbit of the day....

Any leakage past the manifold will allow exhaust to escape, and air to enter......Consider the cat as an "Exhaust" filter. It is responsible for cleaning the exhaust that passes thru it. The PO420 indicates that there is not enough of a difference in Emission levels between Pre and Post cat o2 sensors. In other words, the "Filter" isnt cleaning efficiently. A leaking gasket, a Rot hole, or a "MISSING HONEYCOMB" can easily cause this code. Do you Know for sure the cat has been Gutted? Is this what you were told? or are you going by the 420 code?.....

The missing corners are normal. They provide "Wiggle" room for the bolts when lining up the pipes.

Cats alone dont usually make a drastic difference in exhaust Volume. They do change the tone a bit, but nothing that will be really noticeable.

A fine is a fine....but the cop that stops you will certainly be looking for you again when his quota is due...
 
  #17  
Old 04-28-08, 05:20 PM
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Originally Posted by Unclediezel View Post
A fine is a fine....but the cop that stops you will certainly be looking for you again when his quota is due...

It's illegal to have a "quota".
 
  #18  
Old 04-28-08, 05:26 PM
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It's illegal to have a "quota".
Well.. Its illegal to do what you were doing when he stopped you...so youre even..
 
  #19  
Old 04-28-08, 05:59 PM
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i thought it was gutted because when i tapped on it. It sounds hollow. I just assumed the 420 code was caused by the hollow cat.

I am bring my car into my auto calss to look at it thursday. I am going to probley put a new cat on and posibly a new O2 sensor if it does not come out. i will let you know after it has been fixed. i am hopping this will gime me some better gas mileage and make the engine last longer with it running at normal specs.
 
  #20  
Old 05-01-08, 12:12 PM
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Good news i have the new cat on. Car still sounds the same if not better. The old one was completely nocked out. my Service Engine Soon light is still on but that might be bec of my comp over heating.

Thanks for all the help
 
  #21  
Old 05-01-08, 04:31 PM
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It may take some time for it to go off, but remember, if the cat was that trashed, it probably trashed those O2's.
 
  #22  
Old 05-01-08, 08:29 PM
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you could do some testing with that snap on scanner...or better yet, a labscope. you can also clear the codes with it...
 
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