Check Engine Light P0420 on 2020 Equinox LT - Catalytic Converter Issue?

ClearTheCode admin answer:

The P0420 code on your 2020 Chevrolet Equinox LT at 60,000 miles points to an issue with the catalytic converter's efficiency. While it often indicates a failing catalytic converter, it's crucial to rule out other, less expensive causes first.

Here's a diagnostic approach:

1. Check for Exhaust Leaks: Inspect the exhaust system for any leaks before or near the catalytic converter, especially around the O2 sensors. Leaks can cause incorrect readings.
2. Inspect O2 Sensors: While P0420 specifically points to catalyst efficiency, a failing downstream (post-catalyst) oxygen sensor can sometimes trigger this code by providing inaccurate readings. You can monitor O2 sensor data with a good scan tool to check their activity.
3. Fuel System Health: Issues like misfires or running too rich/lean can damage the catalytic converter over time. Ensure your spark plugs, ignition coils, and fuel injectors are in good condition.
4. Catalytic Converter Test: If the above checks out, the catalytic converter itself might be failing. You can perform a backpressure test to check for blockages, or visually inspect it for damage (though internal damage isn't always visible).

Causes of P0420:

• Failing catalytic converter (most common).
• Faulty downstream oxygen sensor.
• Exhaust leak.
• Engine misfires or other combustion issues leading to unburnt fuel entering the exhaust.
• Contamination from excessive oil consumption or coolant leaks.

When to see a shop:

• If you've ruled out O2 sensor issues and exhaust leaks, and the code persists, it's likely a failing catalytic converter. This is a significant repair that often requires professional installation.
• If you notice a significant drop in fuel economy, a sulfur smell from the exhaust, or a noticeable loss of power, these are strong indicators of a failing catalytic converter that needs immediate attention.