Vision V6-201 3.3L (1993)
warped doors. Replace any part that is found defective.
Thermal or Mechanical Problems Affecting ATC Operation
There are several thermal and mechanical problems that can prevent the ATC system from properly controlling the interior comfort of the vehicle. Refer
to the following list of the most common symptoms and possible causes.
1. The system works fine at night but does not seem to properly control temperatures in partly sunny weather (sun intensity changes). The sun sensor
circuit that has failed open or an improperly installed instrument panel top cover will cause this problem. The body control module cannot detect a
sun sensor or wiring that has an open circuit and no trouble code will be recorded. A sun sensor should have a resistance of 1 to 5 mega ohms. The
instrument top cover can block the sun sensor if it covers too much of the sensor. The top cover when properly installed should allow the sun
sensor to stick out 0.25 inch (measured from the top of the sensor to the cover). Refer to the ATC diagnostics in this manual for repair procedures.
Note that items left on the instrument panel that cover the sun sensor can also affect the operation of the system. Refer to the owners manual for
proper operation.
2. The system seems to cycle the interior temperature too hot or cold (erratic temperature control). This problem can be caused when the in-car
temperature sensor does not sense the temperature of the passenger compartment. This occurs when the in-car temperature sensor aspirator motor
does not operate or if certain instrument panel seals are not properly installed. This problem is more noticeable when the weather is very cold or
hot. Small air leaks of cold or hot air from areas other than the in-car temperature sensor inlet (located behind the name plate) will make the sensor
measure the wrong temperature. Refer to Test 9A to diagnose the in-car temperature sensor.
3. The ATC control panel blue display goes blank and the ATC control operates like a manual NC-heater control. This will occur if there is a
problem with the in-car temperature sensor thermistor or vehicle wiring. Note that an in-car temperature sensor trouble code will be present. Refer
to the in-car temperature sensor diagnostics Test 9A in this manual for repair.
4. The system does not seem to cool the vehicle. This can occur if the ATC-heater unit temperature door is not properly calibrated. Start the engine
and perform the ATC-heater unit door calibration with the DRB. Also check the performance of the ATC-heater unit by performing a partial
charge check with the DRB.
5. The panel outlet temperatures seem to cycle. Use the DRB to position the temperature door at a fixed position. If the panel outlet air does not
cycle, refer to the in-car temperature sensor and ambient sensor diagnostics sections in this manual. If the outlet temperature continues to cycle
excessively, check the operation of the evaporator sensor and the A/C system expansion valve (TXV).
6. The air that leaves the ATC-heater unit does not correspond to what the LEDs indicate on the ATC display. Check to see of the ATC control has a
communications trouble code, and refer to diagnostics in this manual. If no trouble code is present, check the operation of the ATC-heater mode
door actuator linkages.
Auto Headlamps
The headlamps and park/tail lamps will be activated by the BCM when the headlamp switch is in the auto mode. To activate the auto headlamps the
BCM requires that:
1. The headlamp switch is in the "A" position
2. The engine is running
3. The light level sensed through the sun load sensor falls below the calibrated level
Headlamp Time Delay
The headlamp time delay operates when the ignition switch is turned off while the headlamps are still on, and the head lamps are then turned off within
45 seconds after the ignition is off. The BCM will provide a 90-second time delay before turning off the headlamps.
Mechanical Instrument Cluster (MIC)
The body control module sends the angular position of four gauges, the status of seven indicator lamps, the status and dimming of the PRNDL indicator,
the dimming of cruise and low fuel lamps, and odometer stepper motor information to the Mechanical Instrument Cluster (MIC) over the CCD bus when
the ignition is in the "off" (unlock), "run", or "start" positions.
The PRNDL indicator works when the ignition is in the "off , run , or "start" positions; all other MIC features work only when the ignition is in the "run"
position.
On transition of the ignition from the "off" to the "run" position, a bulb check is performed. This consists of activating all CCD-controlled indicator
lamps and all PRNDL segments for approximately 2-4 seconds. The PRNDL bulb check is aborted if the gear selector is moved from the PARK
position, or if the tachometer exceeds 450 rpm.
Overhead Travel Information System/Homelink (OTIS)
The Overhead Travel Information System (OTIS) gives the driver information that supplements the primary gauge instrumentation. OTIS displays
this information on a vacuum fluorescent display (VFD). The OTIS module has four switch inputs. The buttons for these switches are integral to
the OTIS housing. There are two buttons on each side of the display. The buttons are labelled US/M, STEP, C/T, and RESET. The driver selects
and resets display functions through the use of these four buttons.
