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P0420 Code — Meaning, Real Fixes & Costs | MyCarFault
P0420
🟡 Medium Engine system

P0420 — Catalyst System Efficiency Below Threshold B1

12 Driver reports
12 Solved cases
6 Verified fixes
0 Wrong repairs reported

Most Verified Fixes for P0420

Ranked by confidence score — same vehicle matches weighted higher.

Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified
Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified
Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified
Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified
Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified
Downstream O2 sensor replaced first $85. Code returned 1000 miles later. Catalytic converter genuinely worn — replaced with quality aftermarket $320. Passed emissions test. 0%
0 worked · 0 total votes · ⚪ Unverified

Driver Reports — P0420 12 reports

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