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Common Symptoms of a Faulty Catalytic Converter

By R&D
Published on November 18th, 2024

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The catalytic converter is a vital component of a vehicle's exhaust system, tasked with reducing harmful emissions before they are released into the atmosphere. The catalytic converter helps cleanse the vehicle's emissions, ensuring it operates within environmental regulations and standards.

However, when the catalytic converter malfunctions, it can lead to various issues affecting both performance and emissions. This article highlights the common symptoms of a faulty catalytic converter, helping identify potential problems and their underlying causes.

Common Symptoms of a Faulty Catalytic Converter

What Causes Catalytic Converter Failures?

Overheating: Excessive heat generated within the exhaust system can cause the catalytic converter substrate to melt or break down, leading to failure. Additionally, if you inspect the catalytic converter and notice it has turned a glowing red or has blue or purple discoloration, it indicates the converter is damaged due to overheating.

Contamination: Contaminants such as oil or coolant entering the exhaust system., contamination from a failed head gasket, and blow-by gasses from worn piston rings eventually end up in the catalytic converter. These contaminants can “poison” the catalytic converter, reducing its efficiency and effectiveness.

Physical Damage: Impact from road debris or accidents can physically damage the catalytic converter, impairing its ability to function properly.

Age and Wear: Over time, the catalytic converter may deteriorate due to age, wear, and exposure to harsh environmental conditions.

Common Symptoms of a Faulty Catalytic Converter

Malfunction Indicator Light (MIL) or Check Engine Light (CEL) Illuminates

The illumination of the MIL is often one of the first indicators of a potential issue with the catalytic converter. If the downstream oxygen sensor doesn't show a significant reduction in oxygen levels compared to the upstream oxygen sensor, it indicates that the catalytic converter isn't properly converting harmful gasses. The vehicle's onboard diagnostic system may detect abnormal readings, prompting the MIL/CEL to illuminate, alerting the driver to a potential issue with the catalytic converter.

Reduced Engine Performance

A faulty catalytic converter can restrict exhaust flow, leading to reduced engine performance. This may result in decreased acceleration, sluggishness, or a noticeable lack of power, especially during acceleration or under load.

Increased Emissions

As the catalytic converter fails to effectively convert harmful emissions, there may be an increase in tailpipe emissions during vehicle operation. This can lead to a failed emissions test during vehicle inspection or a visible increase in exhaust smoke.

Stalling or Rough Idling

In severe cases of catalytic converter failure, exhaust flow restriction can lead to engine stalling or rough idling. This occurs as the engine struggles to maintain the proper air-fuel ratio and combustion efficiency.

Poor Fuel Economy

A faulty catalytic converter can cause pressure buildup in the exhaust system by restricting the flow of exhaust gasses, leading to a bottleneck effect. This condition causes an increase in fuel consumption by making the engine work harder to overcome the pressure buildup, resulting in poor fuel economy.

Recognizing the symptoms of a faulty catalytic converter is crucial for maintaining vehicle performance, emissions compliance, and overall reliability. Ignoring its problems can lead to more significant engine issues and environmental harm in the long run.

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Identify A Bad Catalytic Converter with Innova Scan Tools

Innova Scan Tools (such as Innova 5510, 5610, etc.) are valuable diagnostic tools that can quickly pinpoint problems with a vehicle’s systems. They can be used for diagnosing and troubleshooting vehicle issues by retrieving and identifying Diagnostic Trouble Codes (DTCs) associated with catalytic converters.

Additionally, using the Innova Scan Tool, you can view and examine catalytic converter values (Live Data) to determine their operational status. The catalytic converter’s normal operating values vary depending on the vehicle.

Notice: The PID names and values related to the catalytic converter differ between makes and models.