Circuit Description
The rear junction block supplies ignition voltage through circuit 141 (BRN). The IPM commands the actuator to move by suppling voltage on the command circuit 1318 (YEL). The command line voltage and motor actions are as follows:
| • | 0 volts moves toward defrost. |
| • | 2.5 volts stops the motor. |
| • | 5 volts moves toward A/C. |
The IPM determines the current position by monitoring the voltage on the feedback circuit 1814 (YEL/BLK). A feedback potentiometer supplies a regulated 5 volt signal by the IPM on circuit 705 (GRY), and a ground from the IPM circuit 1791 (YEL). The pot is gear driven inside the actuator. The feedback voltage is a function of the motor position with a high voltage of 4-5 volts indicating A/C door position. A low voltage of less then 1 volt indicates the defrost position. Operation of the air mix door actuator can be evaluated through scan tool data.
Conditions for Setting the DTC
| • | Ignition is ON. |
| • | Feedback circuit is open or shorted. |
Action Taken When the DTC Sets
| • | A default value of 128 counts will be used by the IPM. |
| • | This default value results in only two positions of the actuator A/C and Defrost being used by the system. |
Conditions for Clearing the MIL/DTC
| • | Using a scan tool. |
| • | A current DTC will clear when the diagnostic runs and does not fail. |
| • | IPM battery voltage is interrupted. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines whether the Body Control Module Diagnostic Symptom Check was performed.
-
This test allows calibration of the actuator by the scan tool.
-
This step determines if the Instrument Panel Integration Module (IPM) is malfunctioning.
-
This step determines if the actuator is operational.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the BCM diagnostic system check performed? | -- | |||
Is the difference between minimum and maximum counts within the specified range? | 200 - 240 counts | Go to Step 3 | Go to Step 4 | |
3 | With a Tech 2 Scan Tool manually command the module (Left) thru its full range - Full Cold to Full Hot ( Engine at normal operating temperature). Are output counts and temperature within normal values? | -- | Go to Step 4 | Go to Step 5 |
4 | With a Tech 2 Scan Tool manually command the module (Right) thru its full range - Full Cold to Full Hot ( Engine at normal operating temperature). Are output counts and temperature within normal values? | -- | Go to Step 6 | Go to Step 9 |
5 |
Is the voltage measured at the specified value? | 5 V | Go to Step 6 | Go to Steap 10 |
6 | Measure voltage at terminal 5, CKT 141 (BRN) and GND. Is the voltage measured above the specified value? | 12 V | Go to Step 7 | Go to Step 10 |
7 | Measure voltage between terminal 7, CKT 1791 (YEL) and terminal 5, CKT 141 (BRN). Is the voltage measured above the specified value? | 12 V | Go to Step 8 | Go to Step 10 |
8 |
Is the voltage measured at the specified value? | 0 - 5 V | Go to Step 9 | Go to Step 10 |
9 | Measure voltage at terminal 9, CKT 1814 (YEL/BLK). Is the voltage measured at the specified value? | 5 V | Go to Step 10 | Go to Step 12 |
10 | Inspect the circuits for an open, or a short condition. Is the repair complete? Was an open or short condition located? | -- | Go to Step 11 | Go to Step 13 |
Repair the open or short condition. Is the repair complete? | -- | Go to Step 20 | -- | |
12 | Short terminal 9 CKT 1814 (YEL/BLK) to ground. Is specified voltage present ? | 0 V | Go to Step 13 | Go to Step 19 |
13 | Connect the electrical connector to the actuator. Is the actuator actual data displayed on the scan tool the specified value? | 5 V | Go to Step 19 | Go to Step 14 |
Using the scan tool, move the actuator to the hot position and to the cold position. Does the actuator move in both directions? | -- | Go to Step 15 | Go to Step 16 | |
15 | Did the actuator actual position feedback change? | -- | Go to Step 20 | Go to Step 18 |
16 | Short terminal 10, CKT 705 (GRY) to terminal 6, CKT 1318 (YEL). Did the actuator move? | -- | Go to Step 17 | Go to Step 18 |
17 | Did the actuator actual position feedback change? | -- | Go to Step 20 | Go to Step 19 |
18 | Replace the actuator. Refer to Mode Actuator Replacement in HVAC System with A/C-Automatic. Is the repair complete? | -- | Go to Step 20 | -- |
19 | Replace the IPM. Refer to Body Control Module Replacement in HVAC System with A/C-Automatic. Is the repair complete? | -- | Go to Step 20 | -- |
20 | Confirm proper operation of the A/C system. Does the system operate normally? | -- | -- |
