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 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 the DTC is a history or an intermittent. Try performing the tests shown while moving the harness wiring and connectors, this can often cause the malfunction to appear. |
| • | When moving related harnesses and harness connectors, visually/physically inspect wiring and connectors for the following: |
| - | Wiring broken inside the insulation. |
| - | Poor mating of the connector halves or a terminal not fully seated in the connector body (backed out). |
| - | Improperly formed or damaged terminals. All connector terminals in the related circuits should be carefully reformed or replaced to insure proper contact tension. |
| - | Poor terminal to wire connection. Inspect for poor crimps, crimping over wire insulation rather than the wire. |
| • | Test the power and ground circuits before replacing the heater and A/C control. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for the voltage supply from the heater and A/C control.
-
This step tests the resistance of the solenoid windings to determine if it is open or shorted.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC Systems Diagnostic System Check? | -- | Go to Diagnostic System Check | |
Does the voltage measure near the specified value? | 12 V | |||
3 |
Does the resistance measure near the specified value? | 0.5 ohms | ||
4 | Locate and repair the open circuit between terminal 26 of the heater and A/C control and harness connector terminal 2 of the water cut-off vacuum solenoid valve. Did you complete the repair? | -- | ||
Measure the resistance of the solenoid valve. Does the resistance measure near the specified value? | 36.4 ohms | |||
6 | Locate and repair the open circuit in CKT 920. Did you complete the repair? | -- | -- | |
7 | Measure the resistance from connector C2 terminal 21 of the heater and A/C control to a good ground. Does the resistance measure near the specified value? | OL | ||
8 | Replace the recirculation vacuum solenoid valve. Did you complete the replacement? | -- | -- | |
9 | Locate and repair the short to ground in CKT 920. Did you complete the repair? | -- | -- | |
10 |
Is a current DTC 30 present? | -- | System OK | |
11 | Replace and program the heater and A/C control. Did you complete the replacement? | -- | System OK | -- |
