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.
Heated Oxygen Sensor Monitor
This monitor applies to DTCs P0133 and P0139. Following conditions must be met during the test:
- Engine coolant temperature must be 176°F (80°C) or more.
- Atmospheric temperature is 14°F (-10°C) or more.
- Selector lever is in "D" range (A/T).
Monitor takes about 5 minutes to complete. To run monitor, use illustration. See Fig 1 . Perform steps as follows:
- Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
- After engine is completely warmed up, turn ignition off.
- Start engine and quickly accelerate vehicle to 35-40 MPH.
- While keeping accelerator pedal position constant (use 4th gear on M/T), keep speed at 35-40 MPH for 120 seconds or more.
- Return vehicle to shop and turn ignition off. Recheck for DTC(s). If any DTC(s) is set, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
Use the Manual With the Right Hardware
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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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