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:
Catalyst System
- P0420
TWC System Low Efficiency (Bank 1)
EGR System
- P0401
EGR System - P0404
EGR System - P0405
EGR Sensor Circuit - Low Voltage - P1404
EGR System (Valve No. 2)
EVAP System
- P0440
EVAP System - P0442
EVAP System - Leak Detected - P0446
EVAP Canister Vent Blocked - P1441
EVAP System Flow During Non-Purge
Oxygen Sensor System
- P0133
HO2S Slow Response - P0140
HO2S Circuit Insufficient Activity (Bank 1; Sensor 2) - P1133
HO2S Insufficient Switching (Bank 1; Sensor 1) - P1134
HO2S Transition Time Ratio (Bank 1; Sensor 1)
Oxygen Sensor Heater System
- P0135
HO2S Heater Performance - P0141
HO2S Heater Performance (Bank 1; Sensor 2)
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.
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