Emissions Codes
704 OBD-II diagnostic trouble codes in this category.
Showing page 2 of 8 (704 codes total)
| Code | Description | Subsystem | Severity |
|---|---|---|---|
| P02E8 | Diesel Intake Air Flow A Position Sensor Circuit Low | Diesel Emissions | High |
| P02E9 | Diesel Intake Air Flow A Position Sensor Circuit High | Diesel Emissions | High |
| P0400 | Exhaust Gas Recirculation Flow Malfunction | EGR System | Medium |
| P0401 | Exhaust Gas Recirculation Flow Insufficient | EGR System | Medium |
| P0402 | Exhaust Gas Recirculation Flow Excessive | EGR System | Medium |
| P0403 | Exhaust Gas Recirculation Circuit Malfunction | EGR System | Medium |
| P0404 | Exhaust Gas Recirculation Circuit Range/Performance | EGR System | Medium |
| P0405 | Exhaust Gas Recirculation Sensor A Circuit Low | EGR System | Medium |
| P0406 | Exhaust Gas Recirculation Sensor A Circuit High | EGR System | Medium |
| P0407 | Exhaust Gas Recirculation Sensor B Circuit Low | EGR System | Medium |
| P0408 | Exhaust Gas Recirculation Sensor B Circuit High | EGR System | Medium |
| P0409 | EGR Sensor A Circuit | EGR System | Medium |
| P0410 | Secondary Air Injection System Malfunction | Secondary Air | Medium |
| P0411 | Secondary Air Injection System Incorrect Flow Detected | Secondary Air | Medium |
| P0412 | Secondary Air Injection System Switching Valve A Circuit | Secondary Air | Medium |
| P0413 | Secondary Air Injection System Switching Valve A Circuit Open | Secondary Air | Medium |
| P0414 | Secondary Air Injection System Switching Valve A Circuit Shorted | Secondary Air | Medium |
| P0415 | Secondary Air Injection System Switching Valve B Circuit | Secondary Air | Medium |
| P0416 | Secondary Air Injection System Switching Valve B Circuit Open | Secondary Air | Medium |
| P0417 | Secondary Air Injection System Switching Valve B Circuit Shorted | Secondary Air | Medium |
| P0418 | Secondary Air Injection System Relay A Circuit | Secondary Air | Medium |
| P0419 | Secondary Air Injection System Relay B Circuit | Secondary Air | Medium |
| P0420 | Catalyst System Efficiency Below Threshold (Bank 1) | Catalytic Converter | Medium |
| P0421 | Warm Up Catalyst Efficiency Below Threshold (Bank 1) | Catalytic Converter | Medium |
| P0422 | Main Catalyst Efficiency Below Threshold Bank 1 | Catalytic Converter | High |
| P0423 | Heated Catalyst Efficiency Below Threshold Bank 1 | Catalytic Converter | Medium |
| P0424 | Heated Catalyst Temperature Below Threshold Bank 1 | Catalytic Converter | Medium |
| P0425 | Catalyst Temperature Sensor Bank 1 | Catalytic Converter | Medium |
| P0426 | Catalyst Temperature Sensor Range/Performance Bank 1 | Catalytic Converter | Low |
| P0427 | Catalyst Temperature Sensor Low Input Bank 1 | Catalytic Converter | Medium |
| P0428 | Catalyst Temperature Sensor High Input Bank 1 | Catalytic Converter | Medium |
| P0429 | Catalyst Heater Control Circuit/Open Bank 1 | Catalytic Converter | High |
| P0430 | Catalyst System Efficiency Below Threshold (Bank 2) | Catalytic Converter | Medium |
| P0431 | Warm Up Catalyst Efficiency Below Threshold Bank 2 | Catalytic Converter | Medium |
| P0432 | Main Catalyst Efficiency Below Threshold Bank 2 | Catalytic Converter | High |
| P0433 | Heated Catalyst Efficiency Below Threshold Bank 2 | Catalytic Converter | Medium |
| P0434 | Heated Catalyst Temperature Below Threshold Bank 2 | Catalytic Converter | Medium |
| P0435 | Catalyst Temperature Sensor Circuit Bank 2 Sensor 1 | Catalytic Converter | High |
| P0436 | Catalyst Temperature Sensor Circuit Range/Performance Bank 2 Sensor 1 | Catalytic Converter | High |
| P0437 | Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 1 | Catalytic Converter | High |
| P0438 | Catalyst Temperature Sensor Circuit High Bank 2 Sensor 1 | Catalytic Converter | High |
| P0439 | Catalyst Heater Control Circuit/Open Bank 2 | Catalytic Converter | High |
| P0440 | Evaporative Emission Control System Malfunction | EVAP System | Low |
| P0441 | Evaporative Emission Control System Incorrect Purge Flow | EVAP System | Low |
| P0442 | Evaporative Emission Control System Leak Detected (Small Leak) | EVAP System | Low |
| P0443 | Evaporative Emission Control System Purge Control Valve Circuit | EVAP System | Low |
| P0444 | Evaporative Emission Control System Purge Control Valve Circuit Open | EVAP System | Medium |
| P0445 | Evaporative Emission Control System Purge Control Valve Circuit Shorted | EVAP System | Medium |
| P0446 | Evaporative Emission Control System Vent Control Circuit | EVAP System | Low |
| P0447 | Evaporative Emission Control System Vent Control Circuit Open | EVAP System | Medium |
| P0448 | Evaporative Emission Control System Vent Control Circuit Shorted | EVAP System | Medium |
| P0449 | Evaporative Emission Control System Vent Valve/Solenoid Circuit | EVAP System | Low |
| P0450 | Evaporative Emission Control System Pressure Sensor | EVAP System | Medium |
| P0451 | Evaporative Emission Control System Pressure Sensor Range/Performance | EVAP System | Low |
| P0452 | Evaporative Emission Control System Pressure Sensor Low | EVAP System | Low |
| P0453 | Evaporative Emission Control System Pressure Sensor High | EVAP System | Low |
| P0454 | Evaporative Emission Control System Pressure Sensor Intermittent | EVAP System | Low |
| P0455 | Evaporative Emission Control System Leak Detected (Gross Leak) | EVAP System | Low |
| P0456 | Evaporative Emission Control System Leak Detected (Very Small Leak) | EVAP System | Low |
| P0457 | Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off) | EVAP System | Low |
| P0458 | Evaporative Emission Control System Purge Control Valve Circuit Low | EVAP System | Medium |
| P0459 | Evaporative Emission Control System Purge Control Valve Circuit High | EVAP System | Medium |
| P0465 | Purge Flow Sensor Circuit | EVAP System | Low |
| P0466 | Purge Flow Sensor Circuit Range/Performance | EVAP System | Low |
| P0467 | Purge Flow Sensor Circuit Low Input | EVAP System | Low |
| P0468 | Purge Flow Sensor Circuit High Input | EVAP System | Low |
| P0469 | Purge Flow Sensor Circuit Intermittent | EVAP System | Low |
| P0470 | Exhaust Pressure Sensor | Exhaust System | Medium |
| P0471 | Exhaust Pressure Sensor Range/Performance | Exhaust System | Medium |
| P0472 | Exhaust Pressure Sensor Low | Exhaust System | Medium |
| P0473 | Exhaust Pressure Sensor High | Exhaust System | Medium |
| P0474 | Exhaust Pressure Sensor Intermittent | Exhaust System | Low |
| P0475 | Exhaust Pressure Control Valve | Exhaust System | Medium |
| P0476 | Exhaust Pressure Control Valve Range/Performance | Exhaust System | Medium |
| P0477 | Exhaust Pressure Control Valve Low | Exhaust System | Medium |
| P0478 | Exhaust Pressure Control Valve High | Exhaust System | Medium |
| P0479 | Exhaust Pressure Control Valve Intermittent | Exhaust System | Low |
| P0480 | Cooling Fan 1 Control Circuit | Cooling Fan | High |
| P0481 | Cooling Fan 2 Control Circuit | Cooling Fan | High |
| P0482 | Cooling Fan 3 Control Circuit | Cooling Fan | Medium |
| P0483 | Cooling Fan Rationality Check | Cooling Fan | Medium |
| P0484 | Cooling Fan Circuit Over Current | Cooling Fan | High |
| P0485 | Cooling Fan Power/Ground Circuit | Cooling Fan | High |
| P0486 | Exhaust Gas Recirculation Sensor B Circuit | EGR System | Medium |
| P0487 | Exhaust Gas Recirculation Throttle Position Control Circuit | EGR System | Medium |
| P0488 | Exhaust Gas Recirculation Throttle Position Control Circuit Range/Performance | EGR System | Medium |
| P0489 | Exhaust Gas Recirculation Control Circuit Low | EGR System | Medium |
| P0490 | Exhaust Gas Recirculation Control Circuit High | EGR System | Medium |
| P0491 | Secondary Air Injection System Insufficient Flow Bank 1 | Secondary Air | Medium |
| P0492 | Secondary Air Injection System Insufficient Flow Bank 2 | Secondary Air | Medium |
| P0493 | Fan Overspeed | Cooling Fan | Medium |
| P0494 | Fan Speed Low | Cooling Fan | Medium |
| P0495 | Fan Speed High | Cooling Fan | Low |
| P0496 | Evaporative Emission System High Purge Flow | EVAP System | Medium |
| P0497 | Evaporative Emission System Low Purge Flow | EVAP System | Medium |
| P0498 | Evaporative Emission System Vent Valve Control Circuit Low | EVAP System | Medium |
| P0499 | Evaporative Emission System Vent Valve Control Circuit High | EVAP System | Medium |
| P04E2 | Crankcase Ventilation Hose Connection Sensor Circuit Low | EVAP System | Medium |
| P0544 | Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 | Exhaust Temp | Medium |
| P0545 | Exhaust Gas Temperature Sensor Circuit Low Bank 1 Sensor 1 | Exhaust Temp | Medium |
About Emissions Codes
This page lists all 704 OBD-II diagnostic trouble codes classified under the Emissions category. These codes are stored by your vehicle's onboard computer when a sensor detects a malfunction in the emissions system. Each code begins with a letter indicating the system (P for Powertrain, B for Body, C for Chassis, U for Network) followed by four digits that identify the specific fault.
When your check engine light comes on, an OBD-II scanner reads these stored codes to help pinpoint the problem. Generic codes (where the second digit is 0) follow the SAE J2012 standard and mean the same thing on every vehicle. Manufacturer-specific codes (where the second digit is 1) may have different meanings depending on the vehicle brand.
Click any code in the table above to see its full description, possible causes, common symptoms, and step-by-step repair guidance. Use the search box to quickly find a specific code within this category.