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My car keeps throwing the same code PO430 Catalyst system

Customer Question
My car keeps throwing the...
My car keeps throwing the same code PO430

Catalyst system efficiency below threshold (bank 2) even after I have taken it in to have 2 of the Catalytic Converter changed along with oxygen sensor replacement. What else could be causing this code to pop back up after only 1 day of driving it since it has returned from the repair shop??? Any help would be appreciated.
Submitted: 7 years ago.Category: Ford
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Answered in 5 minutes by:
2/5/2010
Ford Mechanic: Chuck, ASE Certified Technician replied 7 years ago
Chuck
Chuck, ASE Certified Technician
Category: Ford
Satisfied Customers: 2,101
Experience: 33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
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Which O2 sensors were replaced front,rear or all four?
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Customer reply replied 7 years ago
I think rear but not 100% sure on that.
Ford Mechanic: Chuck, ASE Certified Technician replied 7 years ago

Yeah thats a pretty common mistake. Most people want to replace the rear O2 sensors for these codes but actually this will not fix the problem. The front O2 sensors are the ones that actually need to be replaced. What sets this code is if the switch ratios of the rear sensors start to equal the switch ratio of the front so the first thing that happens is the rear get replaced when actually the front O2 sensors are getting lazy and not switching as often and this is what causes the problem or the cat goes bad one.

There is also a technical service bulletin out from ford to reprogram the computer for this on this vehicle.Here is a copy of the TSB

 

Printable View (29 KB)
TSB
03-24-5
  • DRIVEABILITY - MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED - DIAGNOSTIC TROUBLE CODES P0420 AND/OR P0430
Publication Date: November 20, 2003

FORD:1997 CROWN VICTORIA
LINCOLN:1997 TOWN CAR
MERCURY:1997 GRAND MARQUIS

ISSUE:

Some 1997 Crown Victoria, Grand Marquis and Town Car vehicles may exhibit a malfunction indicator lamp (MIL) on with diagnostic trouble code(s) (DTC'S) P0420 (Catalyst System Efficiency Below Threshold - Bank 1) and/or P0430 (Catalyst System Efficiency Below Threshold - Bank 2).

ACTION:

To service, reprogram the powertrain control module (PCM) to the latest calibration using WDS release B28.4 or higher. Replacement of catalysts is no longer necessary to address the most common causes of this condition.

Obtain an Authorized Modifications Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.

AUTHORIZED MODIFICATIONS

THE FOLLOWING MODIFICATIONS HAVE BEEN MADE:
Reprogrammed Powertrain Control Module (PCM) Per TSB 03-24-5
THESE MODIFICATIONS HAVE BEEN APPROVED, AS APPROPRIATE, BY EPA AND CARB.
DEALER NUMBER:------------------------------------------DATE:

CHANGE AUTHORITY:

FPS 8262 9/78 FORD MOTOR COMPANY PRINTED IN U.S.A.

OTHER APPLICABLE ARTICLES:

NONE

WARRANTY STATUS:

Eligible Under Provisions Of New Vehicle Limited Warranty Coverage And Emissions Warranty Coverage

 

 

I would recommend having the front O2 sensors replaced and the PCM reprogrammed and this should take care of your concern.

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Chuck, ASE Certified Technician
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