The P0422 code on your 2019 Audi Q5 indicates the main catalytic converter on bank 1 is not meeting efficiency thresholds. This code specifically targets the primary (main) catalyst rather than any warm-up or secondary catalysts in the system.
Main vs. Warm-Up Catalysts
Modern exhaust systems often include multiple catalysts. Warm-up catalysts are positioned close to the engine for quick light-off. Main catalysts, located further downstream, handle the bulk of emissions conversion once the system is at operating temperature. P0422 indicates the main catalyst has degraded.
Q5 Exhaust System
The 2019 Audi Q5's 2.0L TFSI engine uses an integrated exhaust manifold and catalyst system. Bank 1 contains cylinder 1 on this four-cylinder engine. The turbocharged engine's exhaust temperatures can stress catalysts, especially if other problems exist.
Why Main Catalysts Fail
Age and mileage cause gradual substrate deterioration. Engine running rich contaminates catalyst surfaces. Misfires send unburned fuel into the catalyst, causing overheating. Oil consumption coats precious metals. Physical damage from road debris affects internal structure. Contaminated fuel containing lead or silicon poisons the catalyst.
Diagnostic and Repair
Use Audi ODIS to monitor catalyst efficiency values. Test oxygen sensor function—false readings cause misdiagnosis. Check for exhaust leaks affecting sensor accuracy. Verify no underlying engine problems caused catalyst damage. Catalyst replacement is expensive; ensure diagnosis is accurate before proceeding.