Without Scan Tool

INTRODUCTION AND GENERAL DESCRIPTION
The self-diagnostic system diagnoses sensors, door motors, blower motors and multiplex communication errors, etc. by system line. Shifting from normal control to the self-diagnostic system is done as follows. Start the engine (turn the ignition switch from "OFF" to "ON") and press VENT switch for at least 5 seconds. The VENT switch must be pressed within 10 seconds after starting the engine (ignition switch is turned "ON"). This system will be canceled by either pressing AUTO switch or turning the ignition switch "OFF". Shifting from one step to another is accomplished by means of rotating temperature switch, as required. Additionally shifting from STEP 5 to AUXILIARY MECHANISM is accomplished by means of pushing BLOWER switch.










STEP BY STEP PROCEDURE

HOW TO INTERPRET THE RESULTS




STEP 1: Checks LEDs and segments
When switch's LED and segments are in good order in STEP 1 mode, the corresponding LED and fluorescent display tube will illuminate.




If LEDs or segments malfunction, LED will not come on or display will show incomplete segment.




STEP 2: Checks each sensor circuit for open or short circuit
Display shows "2 " in STEP 2 mode.
When all sensors are in good order, display shows "20".
It takes approximately 4 seconds to check all sensors.




If a sensor is malfunctioning, the corresponding code No. blinks on display. A short circuit is identified by a blinking "- " mark preceding mode number.




If two or more sensors malfunction, corresponding code Nos. respectively blink two times.




Sensors and abnormalities
If a circuit is opened or shorted, display shows its code No. when input corresponds with any of following conditions.




STEP 3: Checks mode and intake door positions
Display shows "3 "in STEP 3 mode.
When all doors are in good order, display will then show "30 " It takes approximately 20 seconds to check all mode and intake doors.







When abnormalities are detected, display shows a code No. corresponding with malfunctioning part.




If two or more mode or intake doors are out of order, corresponding code numbers respectively blink two times.
If mode door motor harness connector is disconnected, the following display pattern will appear.
31--> 32 --> 33 --> 34 --> 35
If intake mode door harness connector is disconnected, the following display pattern will appear.
36 --> 37 --> 38 --> 39
If any mode door motor position switch is malfunctioning, mode door motor will also malfunction.




STEP 4: Checks operation of each actuator
Display shows "41 " in STEP 4 mode.
When DEFROSTER switch is pressed one time, display shows
"42 " Thereafter, each time the switch is pressed, display advances one number at a time, up to "46 " then returns to "41 ".

During inspection in STEP 4, the auto amplifier will forcefully transmit an output to the affected actuators. The corresponding code Nos. are shown on display as indicated in the table below.
Checks must be made visually, by listening to any noise, or by touching air outlets with your hand, etc. for improper operation.




Operating condition of each actuator cannot be checked by indicators.










STEP 5: Checks temperature detected by sensors, and detects multiplex communication error
Checks temperature detected by sensors
Display shows "51 " in STEP 5 mode.
^ When DEFROSTER switch is pressed one time, display shows temperature detected by ambient sensor.
^ When DEFROSTER switch is pressed second time, display shows temperature detected by in-vehicle sensor.
^ When DEFROSTER switch is pressed third time, display shows temperature detected by intake sensor.
^ When DEFROSTER switch is pressed fourth time, display returns to original presentation "51 ".
If temperature shown on display greatly differs from actual temperature, check sensor circuit at first. Then inspect sensor itself.







Detects multiplex communication error
Display shows "52 " in STEP 5 mode.
[Multiplex communication error between control unit and auto amplifier is detected]

CAUTION:
The auto amplifier memorizes any communication error in the system in a normal control with battery connected. When there is an error, display will be as shown above. When plural errors occur, the display of each error will blink two times for 0.5 second intervals.




If a communication error is displayed, follow the flow chart below to judge if the error occurred in the past or is currently happening.

AUXILIARY MECHANISM: Temperature setting trimmer
This trimmer compensates for differences between temperature setting (displayed digitally) and temperature felt by driver in a range of ±3° C (±6° F).




Operating procedures for this trimmer are as follows:
Starting with STEP 5 under "Self-diagnostic mode", press (blower speed up) switch to set air conditioning system in auxiliary mode. Then, set temperature switch to desired temperature. Temperature will change at a rate of 0.5° C (1° F) each time a switch is turned.
When battery cable is disconnected, trimmer operation is canceled and temperature set becomes that of initial condition, i.e. 0° C (0° F).