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.
Circuit Description
The DTC P0133 Heated Oxygen Sensor (HO2S) Slow Response Sensor 1 diagnostic detects an unresponsive oxygen sensor. The Powertrain Control Module (PCM) continuously monitors HO2S activity. PCM counts the number of times that a rich-to-lean and lean-to-rich response is indicated and adds amount of time required to complete all the transitions. PCM uses this information to determine an average time for each transition. A DTC P0133 will set if the average transition time is too slow.
A lean-to-rich transition is indicated when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich-to-lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly may be faulty and should be replaced. See HO2S OPERATION table.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.