An oxygen sensor slow response or low activity trouble code is almost always a faulty oxygen sensor. There are a few other things to consider before replacing the oxygen sensor. Exhaust leaks upstream or very near the oxygen sensor as well as oxygen sensor heater circuit malfunctions can also set this code.

Engine Performance Diagnostics chapter 5


  • check engine light (P0134)
  • poor gas mileage
  • rough idle
  • runs fine intermittently

fix 50

  • replace faulty oxygen sensor

test shown

  • scan data O2 analysis

Tools used

  • scan tool

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(Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing

Related videos:

Nissan EVAP leak P0455 (vacuum cut valve-bypass valve test):


P0133 O2 Slow Response (2007 Hyundai Tiburon):


What can cause an O2 sensor to read near 5 volts? (Chrysler bias voltage):


Engine runs rich P0172, P0175 from a blown O2 heater fuse (Jeep):


O2 sensor testing (fixed lean) P0174, P0154, P0155 - Mitsubishi:


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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