Circuit Description
The recirculation switch on the control panel is a momentary switch that returns to the rest position after it is pressed to the ON or OFF positions. When it is pressed to the ON position, 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
| • | If a short circuit to battery is detected on a low side driver, the controller automatically protects the low side driver by disabling all low side outputs. |
| • | A short to battery has been detected on CKT 921. |
Action Taken When the DTC Sets
| • | Stores a DTC 29 in the heater and A/C control memory. |
| • | The fault detection process is repeated 3 times at a fixed interval of 70 ms to allow for debouncing. |
| • | The heater and A/C control disables the output internally. |
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 conditions for the fault is no longer present. |
Diagnostic Aids
| • | If the DTC is a history or an intermittent. Try to perform 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: |
| - | Dirt or corrosion on the terminals. The terminals must be clean and free of any foreign material which could impede proper terminal contact. |
| - | Damaged connector body, exposing the terminals to moisture and dirt, as well as not maintaining proper terminal orientation with the component or mating connector. |
| - | Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle. |
| • | Check 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.
-
Tests for voltage to the water cut-off solenoid valve.
-
This step checks for shorted solenoid windings.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC Systems Diagnostic System Check? | -- | Go to Diagnostic System Check | |
Does the test lamp illuminate? | -- | |||
3 |
Did you find and correct the condition? | -- | ||
4 | Repair the coil side feed circuit of the recirculation vacuum solenoid valve. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
5 |
Does the DTC reset? | -- | System OK | |
Measure the resistance of the recirculation vacuum solenoid valve. Does the resistance measure much less than the specified value? | 36.4 ohms | |||
7 | Replace the recirculation vacuum solenoid valve. Did you complete the replacement? | -- | -- | |
8 | Inspect for poor connections at the harness connector for the heater and A/C control. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | ||
9 | Replace and program the heater and A/C control. Did you complete the replacement? | -- | -- |
