I own a 2002 DHS and for the second time am experiencing a failed Catalytic converter. Can anyone tell me what causes the failure? Cadillac dealer refuses to own up to a bad converter which failed about 2 to 3 weeks after the second warranty expired. The first converter was replaced under the 90,000 mile warranty.

 

excessive fuel, lead fuel, fuel additives, rich mixture?
here are some of the common causes ...

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A number of problems could occur to the catalytic converter as the result of an engine that is out of tune. Any time an engine is operating outside proper specifications, unnecessary wear and damage may be caused to the catalytic converter as well as the engine itself. The damage is often the result of an incorrect air/fuel mixture, incorrect timing, or misfiring spark plugs. Any of these conditions could lead to catalytic converter failure or worse.

Excess Fuel Entering Exhaust. The fuel that powers your vehicle is meant to burn in the combustion chamber only. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and light-off when it reaches the catalytic converter. This can super-heat the converter far above normal operating conditions and cause a meltdown. Possible causes are an incorrect fuel mixture, incorrect timing, corroded spark plugs, a faulty oxygen sensor, sticking float, faulty fuel injector or a malfunctioning check valve.

Oil or Antifreeze Entering Exhaust. Oil or antifreeze entering the exhaust system can block the air passages by creating a heavy carbon soot that coats the ceramic catalyst. These heavy carbon deposits create two problems. First, the carbon deposits prevent the catalytic converter from reducing harmful emission in the exhaust flow. And second, the carbon deposits clog the pores in the ceramic catalyst and block exhaust flow, increasing backpressure and causing heat and exhaust to back up into the engine compartment. Your engine may actually draw burnt exhaust gasses back into the combustion chamber and dilute the efficiency of the next burn cycle. The result is a loss of power and overheated engine components. Possible causes are worn piston rings, faulty valve seals, failed gaskets or warped engine components.

Deteriorated Spark Plug or Spark Plug Wires. Spark plugs that don’t fire, or misfire, cause unburned fuel to enter the exhaust system. The unburned fuel ignites inside the converter and could result in a partial or complete meltdown of the ceramic catalyst. Spark plugs and spark plug wires should be checked regularly and replaced if damaged or if wires are worn or cracked.

Oxygen Sensor Not Functioning Properly. An oxygen sensor failure can lead to incorrect readings of exhaust gasses. The faulty sensor can cause a too rich or too lean condition. Too rich and the catalyst can meltdown.




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Also an impact with something in the road. The honeycomb inside is fragile. If your "cat" looks like a muffler and has regular exhaust pipe inlets and outlets, a high performance one can be purchased from www.summitracing.com for around $150

 

That is very bad. Have you found out what had been the cause? See this Catalytic Converter Replacement DIY. You can utilize this when you opt to change it yourself. Hope it will help you.