Disconnect the lower solenoid valve vacuum hose from the vacuum manifold and connect the vacuum pump.
Disconnect the upper solenoid valve vacuum hose from air control valve A.
Disconnect the 2-pin connector near the solenoid valve.
Create a vacuum.
If the valve does not hold vacuum, then it should be replaced.
If the solenoid valve is holding vacuum, then connect the positive battery terminal to the Green/Black terminal of the 2-pin connector and the negative battery terminal to Black.
Next, create a vacuum.
If the solenoid valve holds vacuum, then it should be replaced.
If not, then disconnect the battery from the 2-pin connector.
Next, reconnect the vacuum hose.
Warm up the engine to operating temperature until the cooling fan turns on.
Measure voltage between Green/Black (+) and Cherny (-) terminals on the main wiring harness while the engine is running at approximately 2500 rpm.
If the voltage fluctuates between 0 and 12 volts, then check the vacuum line for proper connection, cracks, blockage, or hose disconnection.
If not, then measure the voltage between Green/Black (+) contact and ground while the engine is running at approximately 2500 rpm.
If the voltage fluctuates between 0 and 12 volts, repair the break in the Black wire between the solenoid valve and point G4.
If not, then you should check for an open Green / Black wire between the solenoid valve and terminal 29 of the control unit. If the wire is normal, then you should refer to the diagnostics section of the inputs of the control modules.