Disconnect the No. 5 solenoid valve vacuum hose from the vacuum manifold and connect the vacuum pump.
Disconnect the #15 solenoid valve vacuum hose from the vacuum manifold and connect a pressure gauge.
Create a vacuum.
If the solenoid valve does not hold vacuum, then 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 a vacuum, see point A). If not - item B).
A) Bring the engine speed up to more than 2000 rpm.
If the pressure gauge does not show vacuum, then the vacuum line should be checked for proper connection, cracks, blockage or hose disconnection.
If the pressure gauge shows a vacuum, disconnect the 8-pin connector on the control box.
Next, measure the voltage between Blue/Yellow (+) and Cherny (-) contacts on the main wiring harness.
If voltage is present, refer to the control module input diagnostics section. 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 Blue/Yellow (+) and Cherny (-) contacts on the main wiring harness.
If battery voltage is present, the solenoid valve should be replaced.
If there is no voltage, then measure the voltage between Blue/Yellow (+) contact and weight.
If there is battery voltage, repair the open in the Black wire between the control box and point G7.
If there is no voltage, then you should check for an open Blue / Yellow conductor between the control box and terminal 25 of the control unit. If the wire is normal, then you should refer to the diagnostics section of the inputs of the control modules.