P0422 2016 GMC Sierra Code - Catalyst 2 Low Efficiency

P0422 indicates that the second catalytic converter in the exhaust system is not functioning efficiently, as detected by the vehicle’s ECM.

Symptoms may include an illuminated check engine light, reduced fuel efficiency, poor engine performance, or a sulfuric smell from the exhaust.

Common causes include a failing catalytic converter, faulty oxygen sensors, exhaust leaks, or engine issues like misfires or burning oil.

While the vehicle may still be drivable, prolonged driving with this code can damage other components and increase emissions. Prompt diagnosis and repair are recommended.

A mechanic will use a scan tool to verify the code, inspect oxygen sensor readings, check for exhaust leaks, and test the efficiency of the catalytic converter.

Repairs may include replacing the catalytic converter, replacing faulty oxygen sensors, fixing exhaust leaks, or addressing engine performance issues.

Repair costs can range from $200 for oxygen sensors to $1,000+ for a catalytic converter replacement, depending on parts and labor.

Yes, a malfunctioning oxygen sensor can give incorrect readings, leading the ECM to interpret the catalytic converter as inefficient.

Fuel additives may temporarily improve catalytic converter performance, but they are not a guaranteed fix for this code.

Ignoring the code can lead to increased emissions, reduced engine performance, and potential damage to the exhaust system or other components.