B0248

CIRCUIT DESCRIPTION
The mode actuator is an electronic stepper motor. The HVAC control module (IPM) supplies power and ground to the actuator. The IPM controls the direction of the mode actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value (9.5 to 12 volts). The IPM determines the door position by counting pulses (voltage fluctuations) caused by the brush to commutator action generated during normal motor operation. The IPM monitors a voltage drop across an internal resistance to detect the pulses. The IPM converts the pulses to counts with a range of 0 to 255 counts.

When a calibration or recalibration procedure is performed, the IPM calculates the mode door travel range. The IPM commands the actuator to each extreme position and counts the total number of pulses. The IPM compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON. This DTC runs during and after the next range check following the setting of DTC B0249.

CONDITIONS FOR SETTING THE DTC
The IPM does not detect any movement of the mode actuator.

ACTION TAKEN WHEN THE DTC SETS
^ The IPM commands the recirculation door to the outside air position.
^ The IPM will recalibrate the mode actuator each time the ignition switch is turned ON.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The DTC will become history if the IPM no longer detects a failure.
^ The history DTC will clear after 50 fault free ignition cycles.
^ The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
^ Inspect the mode door and mode actuator for the following conditions:
- A misaligned mode actuator. Refer to Mode Actuator Replacement.
- Broken or binding linkages or mode door
- Obstruction that prevents the mode door from operating within its full range of motion
- Missing seals to the mode door
- Misaligned seals to the mode door
^ Refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Steps 1-9:

Steps 10-13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the IPM is able to command the mode actuator through its full range of motion.
3. This step verifies that the IPM has successfully calibrated the mode actuator.
4. If the actuator does not move at all, the problem is likely to be the drive circuitry within the IPM, the actuator, or the wiring harness. If the actuator does move, but not within its full range of motion, the problem is likely to be a mechanical binding of the mode door or mode door linkage.
6. This step drives the actuator to the vent position. The mode actuator will not move if the mode door is in already at the extreme position.
7. This step drives the actuator to the defrost position.