P0133

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

OBD-II diagnostic trouble code P0133indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.

Severity Level 3 — Moderate

This code indicates a moderate issue that may affect vehicle performance and fuel economy. Continued driving is possible in most cases, but prompt diagnosis and repair are recommended to prevent further damage.

Common Symptoms

• Check Engine Light on
• Gradually worsening fuel economy over weeks/months
• Sluggish throttle response
• May pass or fail emissions test depending on how slow the sensor is
• Often no noticeable driveability issue initially

Possible Causes

• Aging O2 sensor — response time degrades naturally over 80k-120k miles, this is the most common cause
• Exhaust leak before sensor diluting exhaust gas reaching the sensor
• Contaminated sensor — oil ash from burning oil, coolant from small head gasket leak, or silicone sealant poisoning
• Carbon buildup on sensor element from rich running condition
• Low-quality aftermarket sensor previously installed with poor response characteristics

Common Fixes

• Replace upstream O2 sensor with OEM or high-quality (Denso/NTK/Bosch) sensor ($80-300)
• Repair exhaust leak affecting sensor reading ($50-400)
• Fix oil consumption issue causing sensor contamination ($500-3000 depending on cause)
• Perform fuel injection cleaning to correct rich condition fouling sensor ($80-200)

Estimated Repair Cost

These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.

Explore Repair Costs

Related Discussions

See what other car owners are saying about this code and related repairs.