The BARO sensor is one of the inputs the ECU relies upon to determine whether or not the VTEC solenoid is engaged at 4500 rpm.
Here is a link to the old Helm Shop Manual. It's in PDF format and can be searched.
http://planbmarine.com/wp-content/u...ice-workshop-and-repair-BF175A-BF200A-BF2.pdf
The procedure for testing the BARO sensor starts on page 5-37.
The procedure for testing the VTEC sensor starts on page 5-43.
From page 18-16 in the old Helm shop manual....
VTEC System (BF225A)
The VTEC system switches the valve timing and valve lift between low-and high-speed settings to maximize the amount
of intake air in all ranges, thus exploiting the full potential of the engine throughout its entire operating range from high
speeds to low speeds.
The VTEC arrangement consists of three rocker arms for each cylinder (primary, secondary and mid rocker arms; syn-
chronizing pistons; low-speed high-speed cams; a VTEC solenoid valve; and ECM.
When the engine is operating in the low-speed range, the VTEC solenoid valve is closed, blocking the hydraulic pres-
sure passage to the synchronizing piston incorporated in the rocker arms. Each rocker arm is driven by its low-speed
cam independently of the other rocker arm. When the engine is operating in the high-speed range, the VTEC solenoid
valve opens, allowing hydraulic pressure to be applied to the synchronizing piston. The synchronizing piston then
moves and links the three rocker arms together. As a result, all the rocker arms are moved by the high-lift high-speed
cam that drives the mid rocker arm.
The VTEC system switches from the low-speed cams to the high-speed cams when all of the following conditions are
satisfied.
At least two seconds have elapsed since engine startup.
A forward or reverse gear selection has been made. (The neutral switch is OFF.)
The engine temperature (as indicated by the engine temperature sensor) is -20°C (28.4"F)or higher.
The engine speed is 4,500 rpm or higher.
There is no low-pressure alert. (The high-pressure oil switch is ON.)
The high-pressure oil switch is not faulty.
The system switches back from the high-speed cams to the low-speed cams when the engine speed drops to 4,300 rpm.