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  1. DTC's, Problems & Troubleshooting
    I have a 2005 Buick Lacrosse CXL, 3800 series 3. I have been dealing with P0420 since April. I replace a single part and reset my CEL each time. So far i have replaced both 02 sensors, the catalytic (factory style with new gaskets), the gas cap, and most recently the canister solenoid (located...
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