My Avalanche doesn't get driven alot and this past week I found the battery was completely dead. I jump started it and drove it and all was fine. Now twice it's thrown a P0420 code for Converter Efficiency. I had to replace the Bank 1 O2 Sensor about 6 months ago due to a failed heating element. Other than that this is the only issue I've had. Before I go drop a $1500 on coverters on a vehicle that doesn't even have 50,000 miles on it I am looking for some advice. Any help would be appreciated. ---------- Post added at 03:30 AM ---------- Previous post was at 03:28 AM ---------- Also.. I've owned the vehicle since it was new and it has been well maintained and hasn't had any fuel additives or anything else put in the fuel system that would contaminate the converters.