DTC 030

CIRCUIT DESCRIPTION
When the water cut-off vacuum solenoid valve is activated it allows vacuum to be applied to the hot water control valve. The control valve prevents heated coolant from entering the heater core when the vacuum is applied.

In the air conditioning mode or when cooler air is requested, the heater and A/C control grounds the coil of the water cut-off vacuum solenoid valve. When the ignition switch is in the ON position, battery voltage is supplied from the heater and A/C control to the solenoid. With voltage supplied and ground provided the solenoid energizes, and allows vacuum to flow to the hot water control valve.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
^ Every 200 ms the heater and A/C control continuously monitors CKT 920 for an open or short to ground.
^ CKT 920 stays at or near zero volts.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC 30 in the heater and A/C control memory.
^ The heater and A/C control does not disable the output.

CONDITIONS FOR CLEARING THE DTC
^ The conditions for the fault are no longer present.
^ Using a scan tool.
^ A history DTC will clear after 20 consecutive ignition cycles if the condition for the fault is no longer present.

DIAGNOSTIC AIDS
^ If condition not present, refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Test the power and ground circuits before replacing the heater and A/C control.

TEST DESCRIPTION

Steps 1-13:

The number(s) below refer to the step number(s) on the diagnostic table.
2. Listen for an audible click when the water cut-off vacuum solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the water cut-off vacuum solenoid. The heater and A/C control supplies power to the coil side of the water cut-off vacuum solenoid.
4. Verifies that the heater and A/C control is providing ground to the water cut-off vacuum solenoid.
5. Tests if ground is constantly being applied to the water cut-off vacuum solenoid.