Here is a fun technical fact: the size of an engine in liters is usually equivalent to how many grams of air per second it can intake at idle. The "Real Fix" below from Mitchell 1's SureTrack expert information resource covers a 3.3L Nissan engine that is gasping for 3.3 grams of air per second. Real Fixes are documented issues and solutions from actual shop repair orders.
So, here's the Nissan's story:
A customer with a 2002 Nissan Xterra SE (3.3L) comes into the shop, saying the "check engine" light is on and the engine hesitates upon acceleration. SureTrack's exclusive Common Replaced Parts feature steered the technician in the direction of the Airflow Sensor.
The diagnosis
The technician connected a scan tool and found code P0102 – Mass or Volume Air Flow "A" Circuit Low (Hesitates Upon Acceleration, Replaced Mass Airflow Sensor). He then performed an inspection of the mass airflow (MAF) sensor and related wiring harness, but found no obvious faults. He then monitored live data with the scan tool, and found the MAF sensor read 2.2 grams per second. The MAF sensor should have read 3.3 grams per second at idle.
With a multimeter, he performed a voltage drop test on the MAF sensor ground wire, and found a 0.1V drop across the ground wire. He then measured the voltage at the MAF sensor connector with the multimeter, and found battery voltage was present at the connector.
The tech used the multimeter to check for continuity between the MAF sensor connector, and the powertrain control module (PCM) connector, and found continuity was present between the PCM and MAF sensor connectors. With the engine at operating temperature, he used the multimeter to measure voltage at terminal 54 of the PCM, and found 0.4V. The measured voltage should have been 1.0V to 1.7V.
He then determined there were no circuit faults and the MAF was defective.
The fix
The tech replaced the mass airflow sensor, cleared codes, test drove the vehicle and completed the code set enable criteria. The "check engine" light did not illuminate and no fault codes returned.
The technician was able to resuscitate the Nissan and shared his solution with others, using Mitchell 1's SureTrack.
