With the lower solenoid vacuum hose disconnected from the manifold, connect a vacuum pump. With the upper solenoid vacuum hose disconnected from the 3-way connector and the 2-pin connector near the valve, create a vacuum.
If the valve does not hold vacuum, replace the valve, otherwise connect a pressure gauge to the upper vacuum hose.
Connect battery power to the 2-pin connector as shown in the figure.
Create a vacuum. If the sensor does not show a vacuum, replace the solenoid valve, otherwise, disconnect the battery from the connector.
If the gauge still shows vacuum, replace the valve, otherwise reconnect the 2-pin connector and hose.
Start the engine and let it warm up until the cooling fan comes on. Measure the voltage between terminals 21 (blue/red(+)) and 32 (black(-)) of the control unit (the connector is shown in Fig. 43).
If the voltage differs from 56V, refer to the section on diagnostics of control module inputs, otherwise check the break in the blue/red or black conductors.
