how to troubleshoot P0420 code on my Genesis G70 IG (2017-2023)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Check Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Use a multimeter to test the voltage output of both sensors while the engine is running.
   • Expected voltage: 0.1 to 0.9 volts for the upstream sensor; fluctuating voltage for the downstream.
3. Replace any faulty oxygen sensors as needed.

3. Inspect Catalytic Converter

1. Raise the vehicle using a jack and secure it with jack stands.
2. Visually inspect the catalytic converter for any signs of damage or physical blockage.
3. Use a vacuum gauge to check for backpressure in the exhaust system.
   • Backpressure should be within manufacturer specifications (usually less than 2.5 psi at 2,500 RPM).
4. If the catalytic converter is found to be defective, proceed to replace it.

4. Repair Exhaust Leaks

1. Inspect all joints and connections in the exhaust system for leaks.
2. Tighten any loose bolts and replace gaskets if necessary.
3. Use exhaust sealant to repair small leaks as a temporary measure.

5. Clear Codes and Test

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the vehicle and perform a test drive to monitor for reoccurrence of the code.