# Kawasaki KX450F Service Manual Page 148

Motorcycle.

3-40 FUEL SYSTEM (DFI)
Intake Air Pressure Sensor (Service Code 12)
If the wiring is good, check the sensor for various vacuum.
Remove the intake air pressure sensor [A] and disconnect
the vacuum hose from the sensor.
Connect an auxiliary hose [B] to the intake air pressure
sensor.
Temporarily install the intake air pressure sensor.
Connect a digital meter [C], vacuum gauge [D], the fork oil
level gauge [E] and the measuring adapter to the intake
air pressure sensor.
Special Tools - Fork Oil Level Gauge: 57001-1290
Vacuum Gauge: 57001-1369
Intake Air Pressure Sensor Output Voltage
Digital Meter (+) → W (sensor BL) lead
Digital Meter (–) → BK (sensor GY) lead
Refer to the Self-diagnosis Procedures, connect the 12 V
battery to the main harness.
Measure the intake air pressure sensor output voltage
from various vacuum readings, while pulling the handle
of the fork oil level gauge.
Check the intake air pressure sensor output voltage, us-
ing the following formula and chart.
Suppose:
Pg: Vacuum Pressure (Gauge) of Throttle Body
Pl: Local Atmospheric Pressure (Absolute) measured by
a barometer
Pv: Vacuum Pressure (Absolute) of Throttle Body
Vv: Sensor Output Voltage (V)
then
Pv = Pl – Pg
For example, suppose the following data is obtained:
Pg = 8 cmHg (Vacuum Gauge Reading)
Pl = 70 cmHg (Barometer Reading)
Vv = 3.2 V (Digital Meter Reading)
then
Pv = 70 – 8 = 62 cmHg (Absolute)
Plot this Pv (62 cmHg) at a point [1] on the chart and draw a
vertical line through the point. Then, you can get the usable
range [2] of the sensor output voltage.
Usable range = 3.08 ∼ 3.48 V
Plot Vv (3.2 V) on the vertical line. → Point [3].
Results: In the chart, Vv is within the usable range and
the sensor is normal.
If the reading is out of the usable range, replace the sen-
sor.
If the reading is within the usable range, check the ECU
for its ground and power supply (see ECU Power Supply
Inspection).
If the ground and power supply are good, replace the ECU
(see ECU Removal/Installation).