Recently tripped a CEL. Autozone pulled up code P0420. I replaced the 02 sensor after the 'cat', which was recommended. CEL still came on after reset. Is my 'cat' possibly bad? I was thinking of putting in a bypass component that '3800 performance' sells. It plugs in the existing connector for the 02 and tricks the computer into thinking the CAT is functioning properly.

Any other suggestions would be appreciated, besides replacing the 'cat'....$$$.

 

How does it run?




< CHECK OUT THIS LINK>

 

Check with the dealer, there is recall about the cat. I don't remember the details other than you only take it in if you have a power loss, etc... I think they extended the warranty time also.

 

Car runs fine, but I'm losing gas mileage. If I'm not mistaken the engine will run rich when you have this situation. I guess I will call the dealer.

Thanks for thr replies people !

 

Just because the O2 Sensor is throwing the code does not mean it needs to be replaced.

For example, if your car was running very rich, your O2 sensor would tell the computer there is a rich condition. If the computer sees it is too rich according to parameters in the computer, it will trip the check engine light, as it is effecting emissions output. Replacing the O2 will do nothing, as the new O2 will read the same because there is a problem elsewhere.

I am just using that as an example, not saying that is what is wrong with your car. O2 sensors can throw numerous codes and I am not sure which one that is. Intake leakage, high/low fuel pressure, leakng injector(s), low compression, exhaust leak, plugged cat, short to power or ground in O2 wiring, etc. can all throw O2 sensor codes.

As mentioned, there is an extended warranty on the cat, up to 100,000 miles I believe. At 52,000, mine went out, but I had a major loss of power as my symptom.

Edit- I just saw the link posted to what that code description is... oops. I'd put my money on the cat being bad

 

That is a cat code. There is no recall... but something called a "special policy" on it if the car falls within a certain vin range. Give me the last 8 digits of your vin and I will run it for you.

Usually when the cat goes bad, there is a marked decrease in vehicle performance and sometimes a rattling coming from the converter under load.

Here is a copy of the TSB...

Document ID# 1703629
2001 Chevrolet Monte Carlo


--------------------------------------------------------------------------------


Subject: Special Policy Adjustment - Catalytic Converter #05551 - (09/14/2005)



Models: 2001-02 CHEVROLET IMPALA, MONTE CARLO

2001-02 PONTIAC GRAND PRIX

2001-02 BUICK REGAL

EQUIPPED WITH 3.4L (RPO LA1 - VIN E) OR 3.8L (RPO L36 - VIN K) V6 ENGINE




--------------------------------------------------------------------------------

Condition
Some customers of 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; and Buick Regal model vehicles, equipped with a 3.4L (RPO LA1 - VIN E) or 3.8L (RPO L36 - VIN K) V6 engine, may experience a condition where the vehicle exhaust catalytic converter is replaced due to complaints of lack of power or illumination of the Malfunction Indicator Lamp (MIL). This may be due to the front endcone insulation from the catalytic converter breaking away and blocking the front of the first catalyst brick and preventing the free flow of exhaust gas through the converter.

Special Policy Adjustment
This special policy covers the condition described above for a period of 10 years or 120,000 miles (190,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the customer.

For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after September 15, 2005 are covered by this special policy and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to September 15, 2005 must be submitted to the Service Contract provider.

Vehicles Involved
Involved are all 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; Buick Regal model vehicles, equipped with a 3.4L (RPO LA1 - VIN E) or 3.8L (RPO L36 - VIN K) V6 engine and built within the following VIN breakpoints:

Year
Division
Model
From
Through

2201
Chevrolet
Impala
19100001
19378250

2001
Chevrolet
Monte Carlo
19100001
19378233

2001
Pontiac
Grand Prix
1F100004
1F275188

2001
Buick
Regal
11100004
11338085

2002
Chevrolet
Impala
29100001
29374833

2002
Chevrolet
Monte Carlo
29100016
29374832

2002
Pontiac
Grand Prix
2F100019
2F276927

2002
Buick
Regal
21100001
21288762


Parts Information
Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO).

Part Number
Description
Qty/ Vehicle

10343187
Converter, Catalytic (L36 engine)
1

10343185
Converter, Catalytic (LA1 engine)
1

10328740
Gasket, Catalytic Converter (Converter to I-Pipe, both)
1

15286606
Gasket, Exh Manif Pipe (L36)
1

24505057
Gasket, Exh Manif Pip (LA1)
1


Customer Notification
General Motors will notify customers of this special policy on their vehicles (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly).

Service Procedure
Catalytic Converter Inspection
Begin the inspection by reviewing the condition described by the customer. Refer to "Description and Operation," SI document 657895, to help you determine the correct symptom diagnostic procedure when a malfunction exists. It will also help you determine if the condition described by

 

NYCRISS,

Are there any other special policies in place for the CAT on other Monte year models?

 

Not that Im aware of but if you post up the VIN of the car, I could tell you if there is a policy for it along with any other info about the car you may need.

 

I know this is an old thread, but it sure saved me alot of $$$. Thanks NYCRISS! Turns old my new baby ('02 Intimidator) had one of those faulty cats. I would've never known it was still covered had I not seen this post and called GM, which in turn called the Chevy dealer here and got it all set up. Took her in today and got rid of that ugly check engine light (and a new cat) and didn't cost me a penny.
Thanks!!!

 

Hey Becky! Glad to hear your cat was covered. Big kudos to you for using the search feature rather than just throwing out a question. Your stock just went way up in my book.