Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Inspection/Maintenance System DTCS: Description
The following DTCs are required to set system status to YES:
AIR - Secondary Air Injection (AIR) System
Catalyst System
- P0420: Catalyst System - Low Efficiency.
EGR
- DTC P0401: EGR Flow Insufficient
- DTC P0404: EGR Open Position Performance
- DTC P0405: EGR Position Sensor Circuit - Low Voltage
- DTC P1404: EGR Closed Position Performance
EVAP System
- P0440: Evaporative Emission System
- P0442: Evaporative Emission Control System - Small Leak Detected
- P0446: EVAP Vent System Performance
- P1441: Evaporative Emission System Flow During Non-Purge
Oxygen Sensor
- P0133: HO2S 1 - Slow Response
- P0140: HO2S 2 Circuit - Insufficient Activity
- P1133: HO2S 1 - Insufficient Switching
- P1134: HO2S 1 Transition Time Ratio
Oxygen Sensor Heater
- P0135: HO2S 1 - Heater Performance
- P0141: HO2S 2 - Heater Performance
Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.