Vision V6-201 3.3L (1993)
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windshield wiper / washer
Chime System
DESCRIPTION
The chime system is comprised of an audible chime located internal to the BCM, and is dependent on various inputs to the BCM to operate. These
inputs include key-in ignition switch, exterior lamps, seat belt switch, and speed warning (middle east vehicles only).
CIRCUIT OPERATION
Seat Belt Warning
The seat belt chime is used to indicate to the operator that the seat belt is not fastened when the ignition switch is in the RUN position. The seat
belt switch is normally CLOSED with the seat belt buckled. Circuit G10 is connected between the Body Control Module (BCM) and the switch.
Ground for the switch is provided on circuit Z1. The Z1 circuit terminates at the body ground located at the left kick panel.
Exterior Lamp-on Warning
The exterior lamp ON chime is used to indicate to the operator that the lamps are ON with the drivers door OPEN and the key removed from the
ignition. The Body Control Module (BCM) uses information from circuit L7 to determine if the lamps are ON, and circuit G75 for drivers door
ajar. The chime function will not operate when the headlamp delay feature is active.
Key-In Ignition Warning
The Key-In chime is used to indicate to the operator that the key is in the ignition with the driver's door OPEN. If the key is in the ignition, a
ground path is completed from the G26 circuit at the Body Control Module (BCM), through the CLOSED switch, to the Z1 circuit. The Z1 circuit
is the ground circuit and terminates at the body ground located at the left kick panel.
When the driver's door is open the normally OPEN door ajar switch CLOSES completing a path to ground on circuit G75. The BCM processes
this information and turns on the chime.
A/C Switch Status/Evaporator Temperature Status
When the ignition is in the RUN position, the Body Control Module (BCM) monitors the evaporator temperature and the status of the A/C switch
(manual A/C only) or the current status of the ATC system. Based on this information, the BCM sends a CCD message to the powertrain control module
(PCM) indicating the A/C switch status and the evaporator temperature status.
Automatic Temperature Control (ATC)
The Body Control Module (BCM) provides for automatic temperature control support both through CCD communications and through processing inputs
to determine control for actuators and the blower motor. The BCM interfaces with the ATC display head over the CCD bus. Information on button
activation, blower setting, and temperature setting are supplied to the BCM.
In turn, the BCM supplies the ATC display head with mode information and indication lamp status. The BCM controls blower motor speed by providing
a varying duty cycle of a fixed frequency output (pulse width modulation). There are 14 distinct blower speeds, plus a blower off signal. The body
control module also controls the HVAC mode, temp, and recirculation doors.
ATC Blend, Mode, and Recirculation Door Operation
The DRB trouble codes that indicate a stall failure or a feedback signal failure work together to show what is wrong with the ATC system.
The stall trouble codes mean that the body control module cannot force an actuator to the end of the ATC-heater unit door. Internal problems in the body
control module will set other short-related trouble codes. Having only stall trouble codes indicates that there is a problem with an open or short circuit in
the wiring, a bad actuator, a bad ATC-heater unit door or connecting linkage. It is important that the operation of the ATC-heater unit door be checked if
an actuator is removed. This can be checked by rotating each unit door shaft to confirm that the door will stop at both ends of travel. The actuator itself
has no stops. It must have the ATC-heater unit door to stop travel to pass the stall test.
A feedback signal failure can occur on the blend or mode door. The body control module monitors the feedback signal to check the position of the
actuator. The body control module not only checks the level of the signal but also how much the voltage changes.
A feedback failure can occur if there is a short or open circuit in the wiring, a bad actuator, a bad body control module, a bad ATC-heater unit door or
connecting linkage. The easiest way to diagnose this is to use the DRB to actuate the blend or mode door. Note that the feedback voltage of the actuator
should smoothly change as the actuator is moved. A sudden change in the feedback voltage to a 5.0-volt or a 0.0-volt level indicates the actuator is bad.
A fixed feedback voltage that is less than 5.0 volts or greater than 0.0 volts without a stall failure, or a short failure indicates that the actuator, the
ATC-heater unit door, or a connecting mechanical linkage is jammed preventing movement.
A feedback signal voltage that stays on 5.0 volts or 0.0 volts indicates a wiring or body control module problem.
The feedback failure trouble code can also occur from a lack of actuator travel. This can be checked by confirming that the feedback signal smoothly
changes when the actuator is moved with the DRB. If the signal is OK, the door travel is not correct. The actuator must be removed and the ATC-heater
unit door mechanically checked for proper operation. Typical problems that prevent door movement include screws dropped in the ATC-heater unit or
