CODE 420 : 2000-2005 (other than GXP)

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CODE 420

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DASHAWN1234

Post subject: CODE 420

Posted: Tue Dec 18, 2012 5:34 pm

SLE Member

Joined: Fri Sep 30, 2011 11:43 am
Posts: 59
Year and Trim: 2005 PONTIAC BONNEVILLE SLE

I was told it means to replace the cat. Now my car shuts off without notice. And is very difficult to get started, I mean I have to start it 4 to 5 times to get it started and give it a little gas to keep it idle. I have changed the ICM 1 coil both vent solenoids MAF sensor down stream 02 sensor. What are the symptoms of a plugged cat? Because I dont want to change it and it doesnt resolve the problem

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01bonneSC

Post subject: Re: CODE 420

Posted: Tue Dec 18, 2012 7:20 pm

Certified Bonneville Nut

Joined: Sat May 24, 2008 5:18 pm
Posts: 4938
Location: Sycamore, IL
Year and Trim: 05 Chevy 'Hoe
1997 'maro (3.8L M5)
89 SkiDoo

How many miles on your car?

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00Beast wrote:

Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.

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cprince

Post subject: Re: CODE 420

Posted: Tue Dec 18, 2012 10:27 pm

SE Member

Joined: Wed Sep 12, 2012 1:00 am
Posts: 19
Location: Wakefield QC, Canada
Year and Trim: 2002 SE

Code 420??

lol...

Sounds like some sort of smoking problem.

:rr:

Craig

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01bonneSC

Post subject: Re: CODE 420

Posted: Tue Dec 18, 2012 11:20 pm

Certified Bonneville Nut

Joined: Sat May 24, 2008 5:18 pm
Posts: 4938
Location: Sycamore, IL
Year and Trim: 05 Chevy 'Hoe
1997 'maro (3.8L M5)
89 SkiDoo

PO420 lol

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00Beast wrote:

Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.

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bobjones003

Post subject: Re: CODE 420

Posted: Wed Dec 19, 2012 2:04 am

SLE Member

Joined: Fri Sep 28, 2012 11:46 pm
Posts: 72
Location: Wyoming,mi
Year and Trim: 03 Bonneville se 138500 jbl speakers apline deck

Three-Way Catalyst (TWC) system is used to control emission.
PCM uses signal from Heated Oxygen Sensors (HO2S) to read efficiency
of TWC. PCM will set DTC P0420 if TWC oxygen storage capacity is less
than a predetermined threshold.
That what the code means so. IT could be cat, but it also could be a 02 sensors. it also could be leak in exhaust .
It should actual be safe to drive the car like that, but if was bad 02 you would get poor fuel milage

_________________
2003 Pontiac Bonneville se Mods JBL speakers and apline deck cde-121. More to come in coming months

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DASHAWN1234

Post subject: Re: CODE 420

Posted: Wed Dec 19, 2012 2:14 pm

SLE Member

Joined: Fri Sep 30, 2011 11:43 am
Posts: 59
Year and Trim: 2005 PONTIAC BONNEVILLE SLE

150,000 miles..... the code is P0420 I just figured everyone would know that... I also meant to ask would a plugged cat cause a car to just shut off without notice... Does anyone know how to change an UIM? If so please send pics

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01bonneSC

Post subject: Re: CODE 420

Posted: Wed Dec 19, 2012 2:49 pm

Certified Bonneville Nut

Joined: Sat May 24, 2008 5:18 pm
Posts: 4938
Location: Sycamore, IL
Year and Trim: 05 Chevy 'Hoe
1997 'maro (3.8L M5)
89 SkiDoo

engine/topic1061.html

engine/topic3591.html

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00Beast wrote:

Less off-topic than Lane's Heated Steering wheel, but yeah, back to the topic.

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redzmonte

Post subject: Re: CODE 420

Posted: Wed Dec 19, 2012 6:18 pm

Posts like an L67

Joined: Mon Jun 13, 2011 4:21 am
Posts: 1358
Year and Trim: 2000 SSEI

a bad rear O2 sensor will not make a car fail to idle. my guess is the cat is plugged. you can start by unbolting it and inspecting it to see if it is obviously melted inside. try unboltin the flange just before the cat and see if the car will idle/run with the downpipe unhooked from the cat. will be loud but should idle fine. if you have a lazer temp gun you should be able to see a 100-150* increase in temp from the front of the cat to the back, if it doesnt then again i would say the cat is the issue.

If it is then i would suggest a 2.5" ZZP downpipe, might as well upgrade while fixing it.

Z

_________________
Shane "RedZMonte"
2004 Z16 Z06: Virgin
2000 SSEi: Kenwood DDX512, 3.25" MPS, ZZP DP, PLog, Puck Mount, NGK TR7's, DHP Tuned
1995 Monte Z34: T04e "60" turbo, 42.5# injectors, Borla Catback, OBDII swap, DHP Tuned, Much more...

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Portal » Board index » Mechanical and Maintenance (no chat or performance) » 2000-2005 (other than GXP)

All times are UTC - 5 hours [ DST ]

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