I HIGHLY recommend Sam Postema who owns Lansing Professional Fleet Auto Repair. He's at the edge of downtown, on the corner of Kalamazoo and Larch Streets, kitty corner from Wendy's.....
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DTC Code P0420 P0420 Catalytic Converter Repair
P0420 Catalytic Converter Code Repair & Fix
The dreaded P0420 & p0430 Catalytic Converter Code. I see this code almost more often than the Evaporative P0440 Gas Cap Code.
So how do you fix it?
WHAT IF I TOLD YOU IT IS NOT THE CATALYTIC CONVERTER OR THE OXYGEN SENSORS!
Most auto repair shops and discount auto parts stores will tell you one of the following. Replace Oxygen Sensor or Catalytic Converter. Sounds easy doesn’t it! Then you ask which one? Well lets see todays vehicles have up to four catalytic converters and six oxygen sensors ranging anywhere from fifty dollars to three thousand dollars times the number of converters or oxygen sensors! OUCH!
So what now?
Well you can choose to take a guess and start replacing the cheapest parts first and work your way from there. You may also pay to have you vehicle diagnosed or code scanned at a repair shop or local muffler shop.
Either way you go what happens after the repair is made or the part is swapped out and the service engine light comes back on with the same P0420 Catalytic Converter Code? Do you bring the part back and try again? Take the vehicle back to the repair shop and warranty out the replaced catalytic converter or O2 sensor?
Here is where the fun and expertise comes into play!
You first need to take the vehicle to a reputable auto repair shop not a discount parts store that scans your vehicle for codes and then sells you parts. Remember you get what you pay for and they are in business for one reason only TO SELL PARTS. They do not repair cars!
Secondly, the vehicle needs to be tested with a hand held diagnostic computer interface device. ( A specialty piece of equipment usually ranging in price from five thousand dollars to fifteen thousand dollars!)The trained auto repair technician needs to look at the values and data of all catalytic converters and all oxygen sensors or air fuel sensors. He also needs to verify the presence of any existing codes other than the P0420 code. This piece of equipment will show what the oxygen sensors and catalytic converters are doing with the fuel and air that is being burned by your engine.
Thirdly, evaluate the data. We are looking for specific data. What is each oxygen sensor doing? Are the oxygen sensors in front of the catalytic converters switching high and low? They should be. How high and low? Are they stuck high or low? Are the oxygen sensors behind the catalytic converters staying flat lined or even? As they should be. Or are they following the front oxygen sensors up and down, possibly indicating a faulty catalytic converter? If other codes are found to be stored in the computer those may indicate what is the actual cause of the P0420 code and they also may tell why the catalytic converter failed if in fact that is why the code P0420 has set.
Fourth, evaluate the mechanical condition of the engine. A DIRTY ENGINE CAN NOT RUN CLEAN. What if I told you 50% of all P0420 codes could be fixed by simply cleaning the fuel system and decarbonizing the internal parts of the engine and fuel system! No that crap in a bottle you bought at the parts store will not work. The fuel system will need to be cleaned professionally with a high quality cleaner and a skilled technician who will take the time to clean it right. Systems such as BG or Motorvac work well. The problem with the cheap stuff is it evaporates or burns off before it cleans the engine because it contains mostly alcohol. The commercial grade chemicals have patents on them and are proven daily to work. We also have highly concentrated top engine cleaner that can be used in extreme conditions. This can not be added to fuel tank or will melt fuel pump in days!
We just did another one of these today 06-09-11 on a 2007 Saturn Aura. Cleaned fuel system, scanned data before and after to see what O2 sensors were doing. Prior rear o2 on bank 2 convertor was following up and down like front was. Cleaned now is nice and flat like it should be! Cat is now clean and working as it should be!