How To Check Catalytic Converter With Scan Tool

If you suspect that your vehicle’s catalytic converter is not functioning properly, it’s crucial to take action quickly. Learning how to check a catalytic converter with a scan tool is an essential skill for any car owner or automotive enthusiast. In this comprehensive guide, we’ll walk you through the process step by step, providing you with tips and tricks for using a scan tool effectively. We’ll also cover some frequently asked questions to help you make the most of this diagnostic tool.

Catalytic Converter

A catalytic converter is an essential component of your vehicle’s exhaust system. It serves the following functions:

  • Reducing harmful emissions: The catalytic converter helps reduce toxic gases like carbon monoxide, nitrogen oxides, and unburned hydrocarbons by converting them into less harmful substances such as carbon dioxide and water vapor.
  • Improving fuel efficiency: By promoting more complete combustion, a catalytic converter helps improve your vehicle’s fuel efficiency.
  • Ensuring compliance with emissions regulations: Modern catalytic converters are designed to meet strict emissions standards set by government regulatory bodies.

The Role of a Scan Tool

A scan tool is a diagnostic device used to read and interpret data from your vehicle’s onboard computer. When used correctly, a scan tool can help you identify issues with your catalytic converter by:

  • Accessing diagnostic trouble codes (DTCs): Scan tools can read DTCs related to the catalytic converter and other components of the exhaust system.
  • Monitoring live data: You can use a scan tool to monitor real-time data from various sensors, such as oxygen sensors and exhaust gas temperature sensors, which can provide valuable information about the performance of your catalytic converter.
  • Performing tests: Some advanced scan tools allow you to perform tests on the catalytic converter to assess its efficiency and overall performance.

Choosing the Right Scan Tool

There are several types of scan tools available on the market, including:

  • Basic code readers: These devices can only read and clear DTCs. They are generally more affordable but offer limited functionality.
  • DIY scan tools: These devices offer more functionality than basic code readers, allowing you to access live data and, in some cases, perform tests on the catalytic converter.
  • Professional scan tools: These devices are typically used by professional mechanics and offer the most comprehensive diagnostic capabilities, including advanced testing and programming features.

When choosing a scan tool to check your catalytic converter, consider the following factors:

  • Compatibility: Make sure the scan tool is compatible with your vehicle’s make, model, and year.
  • Functionality: Choose a scan tool that offers the features you need to diagnose and assess the performance of your catalytic converter.
  • Ease of use: Look for a scan tool with an intuitive interface and clear instructions to ensure a smooth diagnostic process.

Step-by-Step Guide: Using a Scan Tool to Check a Catalytic Converter

To use a scan tool to check your catalytic converter, follow these steps:

  • Turn off your vehicle’s engine and ensure it is in park or neutral with the parking brake engaged.
  • Locate your vehicle’s OBD-II (on-board diagnostics) port, which is usually located under the dashboard on the driver’s side.
  • Connect the scan tool to the OBD-II port.
  • Turn on the vehicle’s ignition, but do not start the engine. This will power up the scan tool.

Follow the scan tool’s instructions to read any stored DTCs. Pay particular attention to codes related to the catalytic converter, such as P0420 or P0430.

  • If your scan tool offers live data monitoring, observe the data from the oxygen sensors and exhaust gas temperature sensors. This can help you determine the efficiency of your catalytic converter.
  • If your scan tool has a catalytic converter testing feature, perform the test according to the tool’s instructions.
  • Turn off the ignition and disconnect the scan tool from the OBD-II port.
  • Interpreting Scan Tool Data

To interpret the data provided by your scan tool, consider the following:

  • Diagnostic trouble codes: DTCs related to the catalytic converter can indicate issues such as low efficiency, excessive backpressure, or temperature irregularities.
  • Oxygen sensor data: The readings from the pre-cat and post-cat oxygen sensors can help you assess the efficiency of your catalytic converter. A properly functioning converter will show a steady, low variation in the post-cat sensor readings, while the pre-cat sensor readings will fluctuate more.
  • Exhaust gas temperature sensor data: High exhaust gas temperatures can indicate a clogged or damaged catalytic converter.

Troubleshooting Common Issues

If your scan tool indicates an issue with your catalytic converter, consider the following troubleshooting tips:

  • Inspect the catalytic converter for physical damage: Look for signs of damage, such as dents, cracks, or rust.
  • Check for exhaust leaks: Leaks in the exhaust system can negatively impact the performance of your catalytic converter.
  • Inspect the oxygen sensors: Faulty oxygen sensors can cause issues with the catalytic converter’s performance. Replace any damaged or malfunctioning sensors.
  • Clean the catalytic converter: If your catalytic converter is clogged, consider using a catalytic converter cleaner to dissolve any deposits.


How do I know if my catalytic converter is bad?

Some common signs of a failing catalytic converter include poor engine performance, reduced fuel efficiency, a sulfur-like smell from the exhaust, and the check engine light illuminating.

Can I drive with a bad catalytic converter?

Driving with a faulty catalytic converter can cause further damage to your vehicle, harm the environment, and may result in failing an emissions test. It’s best to address the issue as soon as possible.

Can a catalytic converter be cleaned?

Yes, catalytic converter cleaners are available that can help dissolve deposits and improve the converter’s performance. However, severely clogged or damaged converters may need to be replaced.

How much does it cost to replace a catalytic converter?

The cost of replacing a catalytic converter varies based on the make and model of your vehicle, as well as labor costs. Generally, you can expect to pay anywhere from $600 to $2,000 for a replacement.

How long does a catalytic converter last?

A catalytic converter can last anywhere from 70,000 to 100,000 miles, depending on factors such as driving conditions, vehicle maintenance, and fuel quality.

Can a scan tool tell me if my catalytic converter is clogged?

A scan tool can provide valuable information about the performance of your catalytic converter, but it may not explicitly indicate if the converter is clogged. High exhaust gas temperatures or poor oxygen sensor data can suggest a potential clog.

Do all scan tools work with all vehicles?

Not all scan tools are compatible with all vehicles. Always check the compatibility of a scan tool with your vehicle’s make, model, and year before purchasing or using it.

Can a bad catalytic converter cause a check engine light?

Yes, a failing or malfunctioning catalytic converter can trigger the check engine light. Diagnostic trouble codes related to the catalytic converter, such as P0420 or P0430, may be stored in your vehicle’s onboard computer.

Final Words

Knowing how to check a catalytic converter with a scan tool is a valuable skill for diagnosing potential issues and maintaining optimal vehicle performance. By selecting the right scan tool, interpreting the data it provides, and troubleshooting common problems, you can ensure that your catalytic converter remains in good working condition. Remember to address any issues promptly to prevent further damage to your vehicle and minimize its impact on the environment.

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