Hi guys,
several months ago, we had performance issues with a 2003 Regal GS. Mechanic changed the fuel pump but the prob was a faulty cat converter. We changed that out and all is fine, really. Performance & mpg is great but that darn code 420 keeps popping up about every other week. We clear it out yet it comes back. Is there a way to fool the computer to not give this code?

Was the convertor replaced GM or aftermarket? Common to get this DTC with aftermarket CATs. You can use a post CAT 02 simulator or get a re-programmed PCM module that will inhibit the DTC.

thanks, can you go into more detail on a "post CAT O2 simulator":confused:

All a 02 simulator does is report normal activity that the CAT converter is operating properly and prevents the P0420 DTC. It plugs into the sensor wiring harness and used in lieu of the real sensor. See link below.

Click here (http://www.3800performance.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=O2-EMU&Category_Code=ES_H&Product_Count=16)

What brand CAT converter was installed?