How to Fix a P0420 Check Engine Light with an O2 Sensor Spacer
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A P0420 check engine light usually means your car’s ECU has detected that the catalytic converter isn’t working efficiently. This code is especially common after exhaust modifications or high-mileage use — and it can be frustrating if your vehicle is running fine.
🔍 What Causes P0420?
Your car uses two oxygen (O2) sensors: one before the catalytic converter and one after. If the second sensor sees readings that are too similar to the first, the ECU thinks your catalytic converter isn’t cleaning exhaust gases properly — triggering P0420.
💡 The Fix: O2 Sensor Spacer
An O2 sensor spacer (also called an O2 extender or adapter) creates space between your post-cat O2 sensor and the exhaust flow. This reduces the intensity of the gases the sensor detects — often solving the issue without affecting performance.
At CodeFixParts.com, we offer two types of O2 sensor spacers:
1. Standard Spacer Adapters (No Catalytic Insert)
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Ideal for vehicles with slight CEL issues
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Available in sizes: 32mm, 34mm, 45mm, 46mm, and 50mm
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Thread: M18 x 1.5
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Plug-and-play install
2. Mini Catalytic Converter Adapters
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Built-in catalytic core helps reduce P0420 and P0430 more effectively
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Available in angled and straight options
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Off-road/racing use only
🛠 How to Install:
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Let your car cool down
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Unscrew the post-cat O2 sensor
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Thread in the spacer
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Reinstall the sensor into the spacer
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Clear the code (optional) and drive
⚠️ Legal Note: These parts are for off-road or race use only. They are not EPA approved for highway vehicles.
✅ Final Thoughts
An O2 sensor spacer won’t fix a failing catalytic converter — but it can help eliminate false alarms and annoying check engine lights on modified or aging vehicles.
Explore our full line of O2 sensor spacers and adapters, with free U.S. shipping and stainless steel durability.