A catalytic converter is an emissions control device that reduces toxic gases and pollutants in exhaust from an internal combustion engine into less-toxic pollutants. It is a crucial part of a vehicle’s emissions system, helping to keep the air cleaner. However, like any part, catalytic converters can wear out over time and need to be replaced. Here are some signs that indicate your catalytic converter may need to be replaced soon.
Your Check Engine Light is On
One of the most common signs of a failing catalytic converter is the check engine light coming on. The on-board diagnostics system (OBD) continuously monitors the efficiency of the catalytic converter. If it detects the converter is not working properly, it will trigger the check engine light. Some common diagnostic trouble codes associated with catalytic converter issues are:
- P0420 – Catalyst System Efficiency Below Threshold (Bank 1)
- P0430 – Catalyst System Efficiency Below Threshold (Bank 2)
- P0421 – Warm Up Catalyst Efficiency Below Threshold (Bank 1)
- P0431 – Warm Up Catalyst Efficiency Below Threshold (Bank 2)
While a check engine light can be triggered by a variety of issues, a catalytic converter related code often means it is losing its ability to convert pollutants properly and may need replacement soon.
Reduced Engine Performance
As a catalytic converter ages and becomes restricted or damaged, it can create an exhaust flow restriction. This adds extra load on the engine, reducing power output. You may notice a lack of acceleration and power when trying to speed up or pass other vehicles.
The performance issues tend to gradually get worse over time as the converter further degrades. A failing catalytic converter that severely limits exhaust flow can reduce engine output by 50% or more.
Increased Fuel Consumption
The added exhaust backpressure from a failing converter forces the engine to work harder to expel gases. This can increase fuel consumption, sometimes significantly. You may notice a drop in your usual fuel economy, needing to refill the gas tank more frequently.
How much fuel efficiency drops depends on the specific damage and condition of the converter. But expect a notable increase in fuel usage as the converter deteriorates and restricts flow further.
Sulfur or Rotten Egg Smell
A distinct sulfur or rotten egg-like smell coming from the exhaust can indicate problems with the catalytic converter.
This is caused by excessive amounts of sulfur and hydrogen sulfide gases escaping through the tailpipe instead of being converted by the catalyst. A healthy catalyst would trap these odorous compounds. But a failing one allows the smell through.
Be aware this sulfur smell can accompany converter issues, but other problems like a cylinder misfire or oil leak can also cause it. Diagnosing the check engine codes can help narrow down the cause.
Rattling Sound
Internal pellets or the honeycomb structure inside a catalytic converter can break down over time due to prolonged exposure to heat and vibration.
As debris from the crumbling catalytic material rattles around inside the converter, it creates a noticeable rattling or shaking sound when accelerating. This usually signals the converter needs replacement.
Difficulty Passing Emissions Testing
VEHICLES
| Vehicle Type | Emissions Test Frequency |
|---|---|
| Passenger vehicles less than five years old | Exempt |
| Passenger vehicles five years old or older | Biennial (every two years) |
| Diesel powered vehicles | Annual |
| Hybrid vehicles | Exempt |
Many states require emissions testing periodically on registered vehicles to ensure they meet environmental regulations. Passenger vehicles usually need tested every one or two years once they are five years old or older.
If your catalytic converter is failing, it often cannot properly process emissions during testing. This will lead to a failed smog test. Some states also do visual inspections of the catalytic converter during testing.
Failing an emissions test that your vehicle previously passed can be a tell-tale sign the catalytic converter is no longer working adequately.
What Causes a Catalytic Converter to Fail?
There are a few common causes of catalytic converter failure to be aware of:
- Prolonged Use – Catalytic converters have a finite lifespan. The average OEM catalytic converter will last between 100,000-150,000 miles.
- Oil Contamination – Oil leaking into the exhaust system can coat and damage the catalyst material, reducing efficiency.
- Incorrect Fueling – Using the wrong type of fuel for your engine can lead to converter overheating and failure.
- Engine Misfires – Misfiring cylinders dump unburned fuel into the catalytic converter, causing it to overheat.
- Silicon Contamination – Silicon from internal engine leaks can coat the catalyst and reduce airflow.
Being aware of potential causes can help you prevent premature converter failure. Correcting oil leaks, fixing engine issues, and using the right fuel all help extend the life of your converter.
How Much Does It Cost to Replace a Catalytic Converter?
Catalytic converter replacement costs can vary significantly based on the make and model of vehicle. Used OEM converters are the most economical option. Aftermarket and new OEM converters have a higher upfront cost but typically last longer.
Here are some average replacement costs for common converter types:
| Converter Type | Cost (Parts) | Cost (Parts & Labor) |
|---|---|---|
| Used OEM Converter | $200 – $800 | $400 – $1,000 |
| Aftermarket Converter | $300 – $1,500 | $500 – $1,800 |
| New OEM Converter | $800 – $2,500 | $1,000 – $3,000 |
Labor costs for removal and installation average $150 to $250 for most vehicles. Luxury and hybrid vehicles can be more challenging, running $250 to $500 or more in labor.
Several factors affect OEM converter pricing, including engine size, rare metals used, and whether it’s a single or dual exhaust system. Luxury brands like Mercedes and BMW tend to be among the most expensive.
Should I Replace My Catalytic Converter?
Replacing a faulty catalytic converter is important to keep your vehicle running properly and pass emissions tests. Technically, a failing converter does not completely prevent an engine from running.
However, driving with a bad catalytic converter too long can lead to other problems like loss of power and poor fuel economy. It also allows higher emissions output.
We recommend replacing your converter at the first signs of failure, especially if the check engine light is on. This helps prevent avoidable damage to the vehicle.
Catalytic Converter Replacement Process
Replacing a catalytic converter involves cutting out the old converter and welding in the new one. Here is a typical converter replacement process:
- Lift the vehicle and remove any skid plates protecting the converter.
- Spray penetrating oil on the converter heat shield bolts and exhaust pipe flange nuts. Allow time for the oil to penetrate.
- Loosen the bolts and nuts securing the converter heat shield. Remove the heat shield.
- Loosen the nuts connecting the converter to the exhaust downpipe and tailpipe. Remove old converter.
- Install new converter gaskets on inlet and outlet. Loosely install new converter using supplied hardware.
- Adjust the converter position as needed to fit properly. Tighten hardware to specified torque specs.
- Reinstall heat shield and any skid plates.
- Lower vehicle. Start engine to check for leaks.
The procedure takes 1-3 hours for most vehicles. Some converters are more challenging requiring removal of other components to access them.
DIY vs Professional Replacement
Catalytic converter replacement is possible to DIY on some vehicles, if you have access to jack stands, air tools, and welding/cutting gear. However, there are a few reasons why we recommend professional replacement:
- Proper jacking and securing the vehicle is crucial for safety, and a shop lift simplifies the process.
- Removing rusted exhaust bolts/nuts often requires air tools providing high torque and impact.
- Installing the new converter requires welding skills for precise positioning and optimal exhaust flow.
- Professional shops correct any leaks, debris, O2 sensor damage, etc. before returning the car.
Overall, a skilled technician can replace converters more efficiently and reliably. The cost is reasonable compared to buying tools and equipment. They also handle any troubleshooting needed after installation.
Preventing Catalytic Converter Failure
You can help maximize the lifespan of your original catalytic converter and avoid premature failure by:
- Fixing oil leaks – Oil contamination is very damaging to the converter’s catalyst.
- Addressing engine issues – Unburned fuel from misfires overheats the converter.
- Not ignoring the check engine light – Diagnose and repair any issues before converter damage occurs.
- Maintaining the cooling system – Operating temperatures over 1500°F can destroy the catalyst.
- Using the right fuel – Only use the recommended octane gasoline for your vehicle.
While the converter will still wear out over time, paying attention to proper engine operation and maintenance extends the lifespan significantly.
Conclusion
Catalytic converters play an important role in reducing air pollution from vehicles. But like any component, they degrade over time and need replacement for optimal operation. Being aware of the signs of a failing converter along with average costs allows you to properly maintain your vehicle’s emissions system.
We recommend not delaying too long to replace a bad catalytic converter. Driving with a faulty converter can quickly lead to loss of engine power, reduced fuel economy, and excess emissions. Replacing your failed converter promptly helps avoid further damage and keep your vehicle running cleanly.
