Mazda CX-9 Grand Touring 2009 Manual page 1392

Pin discoloration (blackness)
If there are no problems, proceed to next investigation below.
Standard power supply system inspection for variable resistance type 1
Confirm that the #3 terminal is at 5 V.
If the measured voltage on the #3 terminal is 5 V , inspect the following points on the sensor
connector.
If there is no problem, inspect for the following:
Female terminal opening is loose.
Coupler (pin holder) damage
Pin discoloration (blackness)
If the #3 terminal measures other than 5 V , inspect for the following:
Open or short circuit in wiring harness
Harness/pin crimp is loose or disconnected.
GND system inspection for variable resistance type 1
Confirm that terminal sensor #5 is at 0 V.
If it is at 0 V , inspect the sensor.
If necessary, replace the sensor.
If not, inspect for the following:
Open or short circuit in wiring harness
Female terminal opening is loose causing an open or short circuit in wiring harness
Coupler (pin holder) damage
Pin discoloration (blackness)
Harness/pin crimp is loose or disconnected.
Variable resistance type 2 (mass air flow (MAF) sensor & VSS)
Fig. 14: Variable Resistance Type 2 (Mass Air Flow Sensor & VSS)
Courtesy of MAZDA MOTORS CORP.
2008 Mazda CX-9 Grand Touring
2008 ENGINE Symptom Troubleshooting (MZI-3.7) - Mazda CX-9