Circuit Description
The recirculation switch on the heater and A/C control is a momentary switch that returns to the rest position after it is pressed to the ON or OFF positions. When it is pressed ON, the heater and A/C control grounds the coil of the recirculation vacuum solenoid valve. Battery voltage is supplied from the heater and A/C control to the solenoid, when the ignition is in the ON position. With voltage supplied and ground provided, the solenoid energizes and allows vacuum to flow to the recirculation actuator valve. The heater and A/C control also controls the solenoid valve in the AUTO mode.
Conditions for Setting the DTC
| • | Every 200 ms, the heater and A/C control continuously monitors CKT 921 for an open or short to ground. |
| • | CKT 921 stays at or near zero. |
| • | This fault can only be set with the system OFF. |
Action Taken When the DTC Sets
| • | Stores a DTC 28 in the heater and A/C control memory. |
| • | The heater and A/C control disables the output. |
Conditions for Clearing the DTC
| • | The conditions for the fault are no longer present. |
| • | The DTC can be cleared using a scan tool. |
| • | A history DTC will clear after 20 consecutive ignition cycles if the conditions for the fault are not 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. |
| • | Visually inspect the stepper motor connector and harness for damage, corrosion or water intrusion. |
| • | If condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
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 |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
Does the voltage measure near the specified value? | 12 V | Go to Step 3 | Go to Step 4 | |
3 |
Does the resistance measure near the specified value? | 0.5 ohms | Go to Step 5 | Go to Step 6 |
4 | Test CKT 925/938 of the recirculation vacuum solenoid valve for an open, short to ground or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
Measure the resistance of the recirculation vacuum solenoid valve. Does the resistance measure near the specified value? | 36.4 ohms | Go to Step 7 | Go to Step 8 | |
6 | Test CKT 921 of the recirculation vacuum solenoid valve for an open, short to ground or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | -- |
7 | Measure the resistance from connector C2 terminal 22 of the heater and A/C control to a good ground. Does the resistance measure near the specified value? | OL | Go to Step 10 | Go to Step 8 |
8 | Inspect for poor connections at the harness connector of the recirculation vacuum solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
9 | Replace the recirculation vacuum solenoid valve. Refer to Recirculation Actuator Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
10 | Inspect for poor connections at the harness connector of the heater and A/C control. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
11 |
Important: Perform the set up procedure for the heater and A/C control. Replace the heater and A/C control. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
