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.
2003 Pontiac Sunfire AutomaticFACTORY OEM SERVICE PROCEDURE
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)
EVAP System
- P0440 - EVAP System
- P0442 - EVAP Control System - Small Leak Detected
- P0446 - EVAP Vent System Performance
- P1441 - EVAP System Flow During Non-Purge
Oxygen Sensor
- P0133 - HO2S Slow Response - Sensor 1
- P0140 - HO2S 2 Circuit - Insufficient Activity
- P1133 - HO2S Insufficient Switching - Sensor 1
Oxygen Sensor Heater
- P0135 - HO2S Heater Circuit - Sensor 1
- P0141 - HO2S 2 Heater Circuit
Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
Factory Service Tools
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.