p0420
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Chevrolet · SUVs
Catalyst System Efficiency Below Threshold Bank 1
Quick Answer
Error code P0420 on your Chevrolet SUVs means: Catalyst System Efficiency Below Threshold Bank 1. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
CL14636CL14606Blazer LT 2024Blazer Premier 2024Blazer RS 2024Equinox Activ 2024Equinox LT 2024Equinox RS 2024Suburban High Country 2024Suburban LS 2024Suburban LT 2024Suburban Premier 2024Suburban RST 2024Tahoe High Country 2024Tahoe LS 2024Tahoe LT 2024Tahoe Premier 2024Tahoe RST 2024Tahoe Z71 2024Trailblazer Activ 2024Trailblazer LS 2024Trailblazer LT 2024Trailblazer RS 2024Traverse LS 2024Traverse LT 2024Traverse Premier 2024Traverse RS 2024Traverse Z71 2024Trax Activ 2024Trax LS 2024Trax LT 2024Trax RS 2024CL14526CL14506CK10906CK10706CL14456CL14806CL14416
Likely Causes
How to Fix It
1
Verify the code and check for accompanying misfire or fuel system codes
2
Compare bank 1 upstream and downstream O2 sensor waveforms with a scan tool
3
Inspect the exhaust system for leaks from the manifold to the converter
4
Measure temperature differential across the catalytic converter (inlet vs. outlet)
5
Replace the catalytic converter if confirmed as failed
Pro Tip
This issue typically requires professional diagnosis. Attempting this fix without proper training could cause further problems.
Parts You May Need
Catalytic converter (bank 1)
Downstream O2 sensor (bank 1 sensor 2)
Exhaust gaskets and hardware
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