In the past week or so, my Z28 quickly developed a loud rattling noise that comes from underneath the car. It's most audible at low speeds, but I figure that's just because it's drowned out by other sounds.

Last Friday, my Service Engine Soon light came on. I took it down to AutoZone and had them read and clear it. The result:

DTC P0422 Catalyst System Low Efficiency Bank 1

When it had come on, I had been driving through a lot of deep puddles, and I thought that maybe all of the water had brought the catalytic converter's temperature down and reduced its efficiency. I figured that if it was a big problem, the code would come back shortly.

Today, it came back. Same code.

So, I put the car up in the air and climbed underneath with the engine idling so that I could locate the rattle. It seems to be coming from the drivers side of the Y-pipe, maybe 6" behind the cat.

I suspect that the cat is breaking up inside, and that there's a loose piece of metal inside the exhaust pipe.

Anyone have any other ideas before I tear apart the exhaust? Also, anyone want to sell me a used but functional LS1 catalytic converter for cheap?

 

Your camaro is an 02' right? I have an 02 z28 and I have a paper from a while back talking about the recall on the cats so if you still have the stock cats on there you should be able to get a new one for free.

 

Yeah, it's an '02 (see sig). Thanks for reminding me. I'll look up the recall and see if it applies to me.

EDIT: It was a technical service bulletin, not a recall. Here is the text of the TSB:

SPECIAL COVERAGE ADJUSTMENT #05513 - NOVEMBER 27, 2006

* · Some customers of 2000-02 Chevrolet Camaro and 2000-02 Pontiac Firebird model vehicles, equipped with a 5.7L V8 (RPO LS1 – VIN G) engine, may experience a failure of the left or right catalytic converter.
* · This special coverage covers the condition described above for a period of 10 years or 120,000 miles (193,000 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 November 27, 2006 are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to November 27, 2006 must be submitted to the Service Contract provider.
* · Refer to Special Coverage Adjustment #05513 for further information.

My car is included. I called my local dealer and I have an appointment for Monday. Thanks for the tip!