It's great that the check engine light has not turned on yet since you've replaced the oxygen sensor. Hopefully the repair(s) you made corrected the problem. Driving 50 miles however is not enough to get the monitors to complete, and at times the drive cycle must be completed several times in order for all the parameters to be met.
Typically driving a few hundred miles over the course of a week, in both highway and city conditions, is enough to get the emission monitors to run. Usually the required drive cycle parameters are met over the course of 200-300 miles. However, due to individual driving habits, the criteria required to run a monitor may not always be met; and a Nissan Xterra drive cycle must be performed. Follow the Nissan Xterra drive cycle we've indicated below carefully.
Take extra caution while performing drive cycles on public roadways. If you think you will be unable to follow the Nissan Xterra Drive Cycle below safely, seek the assistance of a smog check repair station or Nissan dealership. Perform the drive cycle at your own risk.
Nissan Xterra Drive Cycle (Driving Pattern)
Pre-Conditioning Requirements:
Ensure the MIL (malfunction indicator lamp) is not on.
Gas tank fuel level must be between 15% and 85% at all times.
Drive cycle must start while engine is cold. Best performed in the morning, after being parked overnight. The actual requirement is that the engine be between 68 and 86 degrees F prior to the start of the drive cycle.
Drive Trace:
A. Start your vehicle and idle engine until coolant temperature reaches 160F (until normal operating temperature is reached). Usually 20 minutes at idle will accomplish this.
B. Using a timer, idle the engine for an additional 1 1/2 minutes.
C. Begin driving. Accelerate smoothly to 56 mph with the transmission in (D) and overdrive ON, then release gas pedal and coast for 10 seconds.
D. Accelerate to 56 mph and maintain speed for at least 10 minutes. Use smooth and quick acceleration and maintain speed as constant as possible.
E. Stop and idle your Nissan Xterra for 10 seconds.
F. Accelerate to 25 mph in 10 seconds and hold gas pedal steady for 20 seconds. Use smooth and quick acceleration and maintain speed as constant as possible.
G. Repeat steps E and F eight (8) times. Decelerate (coast down) to 15 mph and then drive for 13 minutes at speeds between 15mph and 35mph.
H. Accelerate to 53-56 mph and maintain speed for at least 6 minutes. In this step it is more important to maintain accelerator pedal position than speed. Therefore you are allowed 3 mph fluctuation in speed, but must try and keep the gas pedal steady.
- End of Drive Cycle -
If all emissions systems are functioning properly, completing the drive cycle above will set the emission monitors (also known as readiness flags) required to pass the smog check. When visiting a smog station explain to the technician that you've been attempting to complete a drive cycle prior. They can check the monitor(s) status prior to actually administering the emissions inspection.
