July 10

2001 Nissan Pathfinder – MAF Sensor Replacement

Auto Repair, Nissan

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MAF sensor replacement on a 2001 Nissan Pathfinder, brought to us by a client from Burnaby BC is today’s featured service.

Nissan Pathfinder
2001 Nissan Pathfinder

MAF is short for Mass Airflow Sensor, and its function is to measure the flow and density of the air entering your car’s engine. It is one of the major inputs used by the engine computer to determine the amount of fuel to inject for proper combustion.

Our featured 2001 Nissan Pathfinder was brought to us to repair an AirCare failure. This was an interesting case in that the HC and CO levels were very low but the NOx was exceptionally high: 4 times above the fail point.

Experience in emission repairs repairs told us that this engine was running very lean: too little fuel was being injected for the amount of air being sucked into the engine. There are several things that can cause this. As always we performed a thorough diagnosis and found the culprit to be a bad MAF sensor.

Many AirCare failures cause no noticeable driveability issues. That was not the case with this vehicle. When accelerating moderately there was a distinct lack of power and with the gas pedal floored the engine bogged down completely.

After installation of the new MAF sensor proper engine power was restored. We took the vehicle to AirCare where it passed with excellent readings. Interestingly enough you can see, by looking at the test results that the CO and HC are higher. While this may seem like a bad thing it is not: with good combustion and properly functioning emission equipment these are perfect numbers.

Nissan Pathfinder
AirCare results for our 2001 Nissan Pathfinder. Although the failed test (on bottom) has exceptionally low HC and CO, the excessive NOx is a huge problem. Note how low the NOx is after repairs. While the CO is much higher after repairs this indicates a healthy number and is far below the fail point of 8.08 grams per second.

For more about the Nissan Pathfinder click here http://en.wikipedia.org/wiki/Nissan_Pathfinder

For more about Mass Airflow Sensors click here http://en.wikipedia.org/wiki/MAF_sensor

Nissan Pathfinder
Old MAF sensor

About the author 

Bernie Pawlik

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