Check that the manifold absolute pressure sensor has no deformation, cracks or other damages.
Connect dry-cell battery positive terminal to terminal No. 3 and dry-cell battery ground terminal to terminal No. 1, circuit tester positive terminal to terminal No. 2 and the circuit tester negative terminal to terminal No. 1.
NOTE:
- Use new dry-cell batteries.
- Using circuit tester, check the voltage of a single dry-cell battery is 1.6 V or more. And also check the voltage of three batteries in series is between 4.8 V and 5.2 V.
  
  Fig 1: Checking Voltage Of Single Dry-Cell Battery Using Circuit Tester
  Courtesy of SUBARU OF AMERICA, INC.

Check the voltage at a normal atmospheric pressure.

NOTE: The atmospheric pressure at higher altitude is lower than normal. Therefore, the voltage is lower than the standard value.

DRY-CELL BATTERY VOLTAGE TERMINALS REFERENCE CHART

Terminal No.	Standard
2 (+) and 1 (-)	Approx. 4.2 V (when 25°C (77°F))

Connect the Mighty Vac to the pressure port (A) of manifold absolute pressure sensor.

Fig 2: Manifold Absolute Pressure Sensor Pressure Port
Courtesy of SUBARU OF AMERICA, INC.
Check the voltage when generating vacuum and positive pressure using Mighty Vac.
CAUTION: Do not apply vacuum of less than -88 kPa (-0.9 kgf/cm² , -12.8 psi). Doing so may damage the manifold absolute pressure sensor.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Manifold Absolute Pressure Sensor: Inspection