Catalytic Converter Issues : Guide to Diagnose and Repair

A catalytic converter issue may be causing your engine light and associated OBD codes (CEL,MIL,DTC).  Through my experiences, I’ve learned how to identify, troubleshoot, diagnose, and fix these problems. Here’s a simple guide to help you do the same.

What Does it do?

It reduces harmful emissions by converting them into less harmful substances using heat.  This component reduces environmental pollution.

Identifying Issues

Common signs of catalytic converter issues include reduced engine performance, increased fuel consumption, and a sulfur-like smell.  Your car’s check engine light may also turn on.  An engine light alone isn’t enough, see below for relevant OBD codes.

Check for recalls.

Troubleshooting

Start by visually inspecting the converter for any signs of physical damage or discoloration.  A rattling sound from the exhaust system might suggest a failing catalytic converter.

Diagnosing Catalytic Converter Issues

Connect an On-Board Diagnostics (OBD-II) scanner to check for related trouble codes.  The following are OBD codes that indicate issues:

• P0420 – Catalyst System Efficiency Below Threshold (Bank 1)
• P0421 – Warm Up Catalyst Efficiency Below Threshold (Bank 1)
• P0422 – Main Catalyst Efficiency Below Threshold (Bank 1)
• P0423 – Heated Catalyst Efficiency Below Threshold (Bank 1)
• P0424 – Heated Catalyst Temperature Below Threshold (Bank 1)
• P0430 – Catalyst System Efficiency Below Threshold (Bank 2)
• P0431 – Warm Up Catalyst Efficiency Below Threshold (Bank 2)
• P0432 – Main Catalyst Efficiency Below Threshold (Bank 2)
• P0433 – Heated Catalyst Efficiency Below Threshold (Bank 2)
• P0434 – Heated Catalyst Temperature Below Threshold (Bank 2)

Here’s a list of all the OBD codes.

Common Catalytic Converter Failures

A clogged converter can cause engine stalling or misfiring.  Excessive heat can damage the converter’s internal structure.

Prevention

• Regular Maintenance: Timely oil changes.
• The Right Fuel: Use the recommended fuel type for your vehicle.
• Catalytic Converter Cleaner: These are added to your fuel tank and work during normal engine operation.
  • Cleaner in Your Fuel Tank: Follow the instructions. Usually, add it to a nearly empty tank before filling up.
  • Drive: After adding, drive for a set amount of time, typically around 30-50 miles.
  • Highway Driving: Recommended to drive at highway speeds. Creates a higher exhaust temperature burning off deposits in the converter.
  • Professional Inspection: If the cleaner doesn’t help, have a professional mechanic inspect the catalytic converter. Sometimes, internal damage or severe clogging might require mechanical intervention or replacement.

Final Thoughts

Prevention is better than cure, so regular maintenance is key. When problems do arise, diagnosing and fixing them yourself will save you time and money.  Always use a professional mechanic if you’re not comfortable.