🔥 20+ Codes & Counting

Complete OBD2 Codes List

Every check engine code explained in plain English. Find your code, understand what it means, and get a free AI-powered diagnosis with repair cost estimates.

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20
OBD2 Codes
7
Categories
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Engine & Misfire Codes

4 codes
P0300 Random/Multiple Cylinder Misfire Detected → P0301 Cylinder 1 Misfire Detected → P0304 Cylinder 4 Misfire Detected → P0340 Camshaft Position Sensor Circuit Malfunction →
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Emissions & EVAP System

8 codes
P0420 Catalytic Converter Efficiency Below Threshold (Bank 1) → P0430 Catalytic Converter Efficiency Below Threshold (Bank 2) → P0401 Exhaust Gas Recirculation Flow Insufficient → P0442 EVAP System Leak Detected (Small Leak) → P0446 EVAP System Vent Control Circuit Malfunction → P0455 EVAP System Leak Detected (Large Leak) → P0456 EVAP System Leak Detected (Very Small Leak) → P0440 Evaporative Emission Control System Malfunction →
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Fuel System Codes

4 codes
P0171 System Too Lean (Bank 1) → P0172 System Too Rich (Bank 1) → P0174 System Too Lean (Bank 2) → P0128 Coolant Temperature Below Thermostat Regulating Temp →
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Sensor & Electrical Codes

4 codes
P0131 O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1) → P0325 Knock Sensor 1 Circuit Malfunction (Bank 1) → P0500 Vehicle Speed Sensor Malfunction → P0507 Idle Control System RPM Higher Than Expected →

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Related Resources

Guide
How to Read OBD2 Codes: Step-by-Step
Learn exactly how to pull codes from your car using a Bluetooth scanner or code reader.
Popular Code
P0420 — Catalytic Converter
The most-searched check engine code. Full diagnosis guide with cost breakdown.
Popular Code
P0300 — Random Misfire
Multiple cylinder misfire can damage your catalytic converter. Here's how to fix it.
Feature
Live OBD2 Data Monitoring
Catch problems before the check engine light — real-time sensor data, 24/7.
Guide
Most Common Check Engine Light Codes
Top 10 codes that trigger the check engine light, and what to do about each one.
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All Codes at a Glance

Code Description Category Learn More
P0300 Random/Multiple Cylinder Misfire Engine Diagnose →
P0301 Cylinder 1 Misfire Detected Engine Diagnose →
P0304 Cylinder 4 Misfire Detected Engine Diagnose →
P0420 Catalytic Converter Efficiency Below Threshold (Bank 1) Emissions Diagnose →
P0171 System Too Lean (Bank 1) Fuel Diagnose →
P0172 System Too Rich (Bank 1) Fuel Diagnose →
P0174 System Too Lean (Bank 2) Fuel Diagnose →
P0455 EVAP System Leak Detected (Large Leak) Emissions Diagnose →
P0128 Coolant Temperature Below Thermostat Regulating Temp Fuel Diagnose →
P0131 O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1) Sensors Diagnose →
P0446 EVAP System Vent Control Circuit Malfunction Emissions Diagnose →
P0401 Exhaust Gas Recirculation Flow Insufficient Emissions Diagnose →
P0507 Idle Control System RPM Higher Than Expected Sensors Diagnose →
P0325 Knock Sensor 1 Circuit Malfunction (Bank 1) Sensors Diagnose →
P0500 Vehicle Speed Sensor Malfunction Sensors Diagnose →
P0340 Camshaft Position Sensor Circuit Malfunction Engine Diagnose →
P0442 EVAP System Leak Detected (Small Leak) Emissions Diagnose →
P0430 Catalytic Converter Efficiency Below Threshold (Bank 2) Emissions Diagnose →
P0456 EVAP System Leak Detected (Very Small Leak) Emissions Diagnose →
P0440 Evaporative Emission Control System Malfunction Emissions Diagnose →
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