Disconnect the solenoid valve vacuum hose No.5 from the vacuum manifold and connect the vacuum pump.
Disconnect the solenoid valve vacuum hose #15 from the vacuum manifold and connect a pressure gauge.
Create a vacuum.
If the solenoid valve does not hold vacuum, it should be replaced.
If the valve holds a vacuum, then you should warm up the engine to operating temperature until the fan turns on, and pump it out to vacuum at idle.
If the pressure gauge shows the presence of a vacuum, then see point A). If not, then point B).
A) Increase engine speed to more than 2000 rpm.
If the pressure gauge does not show vacuum, then the vacuum line should be checked for proper connection, cracks, plugs, or disconnected hoses.
If the pressure gauge shows a vacuum, then the 8-pin connector on the control box should be disconnected.
Next, measure the voltage between the Blue/Yellow (+) and Black (-) terminals on the main wiring harness.
If there is voltage, then you should refer to the section on diagnostics of control module inputs. If there is no voltage, then the solenoid valve should be replaced.
B) Disconnect the 8-pin connector on the control box.
Measure the voltage between the Blue/Yellow (+) and Black (-) terminals on the main wiring harness.
If there is battery voltage, then the solenoid valve should be replaced.
If there is no voltage, then measure the voltage between the Blue/Yellow (+) contact and ground.
If there is battery voltage, then you should repair the break in the Black wire between the control box and point G7.
If there is no voltage, then you should check for a break in the Blue/Yellow wire between the control box and terminal 25 of the control unit. If the wire is normal, then you should refer to the section on diagnostics of control module inputs.