Air Conditioning System (Diagnostics - Introduction): Overview Lexus IS II facelift 2

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1. PRECAUTION FOR DISCONNECTING CABLE FROM NEGATIVE BATTERY TERMINAL NOTE: When disconnecting the cable from the negative (-) battery terminal, initialize the following system after the cable is reconnected. System Name See Procedure Parking Assist Monitor System Refer to «INITIALIZATION [08/2012 - ]»(ref-606329-S33601054862014032500000)
2. DO NOT HANDLE REFRIGERANT IN AN ENCLOSED AREA OR NEAR AN OPEN FLAME
3. ALWAYS WEAR EYE PROTECTION
4. BE CAREFUL NOT TO GET LIQUID REFRIGERANT IN YOUR EYES OR ON YOUR SKIN If liquid refrigerant gets in your eyes or on your skin: Wash the area with lots of cold water. WARNING: Do not rub your eyes or skin. Apply clean petroleum jelly to the skin. Go immediately to a hospital or see a physician for professional treatment.
5. NEVER HEAT CONTAINER OR EXPOSE THE CONTAINER TO OPEN FLAME
6. BE CAREFUL NOT TO DROP CONTAINER OR APPLY PHYSICAL SHOCKS TO IT
7. DO NOT OPERATE COMPRESSOR WITHOUT ENOUGH REFRIGERANT IN REFRIGERANT SYSTEM If there is not enough refrigerant in the A/C system, oil lubrication will be insufficient and the compressor may be damaged. Necessary care should be taken to avoid this.
8. DO NOT OPEN HIGH PRESSURE MANIFOLD VALVE WHILE COMPRESSOR IS OPERATING Open and close only the low pressure valve. If the high pressure valve is opened, refrigerant flows in the reverse direction causing the charging cylinder to rupture.
9. BE CAREFUL NOT TO OVERCHARGE SYSTEM WITH REFRIGERANT If refrigerant is overcharged, it causes problems such as insufficient cooling, poor fuel economy, engine overheating, etc.
10. DO NOT OPERATE ENGINE AND COMPRESSOR WITH NO REFRIGERANT WARNING: Doing so may damage the inside of the compressor because the compressor parts always move regardless of whether the A/C system is turned on or off.
11. SUPPLEMENTAL RESTRAINT SYSTEM (SRS) This vehicle is equipped with an SRS (Supplemental Restraint System) such as the driver, front passenger, side, and curtain shield air bags. Failure to carry out service operation in the correct sequence could cause the SRS to unexpectedly deploy during servicing, possibly leading to a serious accident. Before servicing (including removal or installation of parts, inspection or replacement), be sure to read the precautionary notices. Refer to «PRECAUTION [08/2012 - ]»(ref-606516-S09770350952014032500000).
12. GENERAL PRECAUTION While using the battery during inspection, do not bring the positive and negative tester probes too close to each other as a short circuit may occur.

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1. *1: w/ Multi-display
2. *2: w/o Multi-display

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1. GENERAL The air conditioning system has the following controls: Control Outline Neural Network Control This control is capable of effecting complex control by artificially simulating the information processing method of the nervous system of living organisms in order to establish a complex input / output relationship that is similar to a human brain. Automatic Recirculation Control Automatically changes the air inlet mode to the fresh air or recirculation air mode according to the level of harmful elements in the outside air, cabin temperature, and outside temperature. Micro Dust and Pollen Filter Mode Control Activated by operation of the micro dust and pollen filter mode switch, this control switches the air vent to FACE mode and sends air which has passed through the clean air filter to the area around the upper part of the bodies of the driver and front passenger. Outlet Air Temp. Control Based on the temperature set at the temperature control switch, the neural network control calculates the outlet air temperature based on the input signals from various sensors. The output air is filtered by the clean air filter in order to remove pollen. The temperature setting for the driver and front passenger is controlled independently in order to provide a separate vehicle interior temperature for the right and left side of the vehicle. Thus, air conditioning that accommodates the occupants' preferences has been realized. Blower Control Controls the blower motor in accordance with the airflow volume that has been calculated by the neural network control based on the input signals from various sensors. Air Outlet Control Automatically switches the air outlets in accordance with the outlet mode that has been calculated by the neural network control based on the input signals from various sensors. In accordance with the engine coolant temperature, outside air temperature, amount of sunlight, required blower, outlet temperature, and vehicle speed conditions, this control automatically switches the blower outlet to foot/defroster mode to prevent the windows from becoming fogged when the outside air temperature is low. Air Inlet Control Automatically controls the air inlet control damper to achieve the calculated outlet air temperature that is required. Drives the air inlet control servo motor according to the operation of the air inlet control switch and moves the dampers to the FRESH or RECIRC position. Compressor Control This control turns OFF the magnetic clutch of the A/C compressor when the blower motor is turned OFF when the engine coolant temperature is below a predetermined value, an abnormal refrigerant pressure has been detected, or the discharge temperature of the evaporator is below a predetermined value (evaporator too cold). A/C amplifier turns the compressor off if the engine coolant temperature becomes abnormally hot (115 °C (239 °F) or above) when driving under a high load. Glow Plug Control The A/C amplifier and ECM operate two glow plugs in the engine coolant to reduce the period of increased fuel consumption due to a cold engine, and to improve heater performance. Rear Window Defogger Control Switches the rear defogger and outside rear view mirror heaters on for 15 minutes when the rear defogger button pressed and switches them off if the button is pressed while they are operating. Outside Temperature Indication Control Based on the signals from the ambient temperature sensor, this control calculates the outside temperature, which is then corrected in the A/C amplifier, and shown in the display and navigation module display. Self-Diagnosis A DTC (Diagnostic Trouble Code) is stored in the memory when the A/C amplifier detects a problem with the air conditioning system.
2. NEURAL NETWORK CONTROL In previous automatic air conditioning systems, the A/C amplifier determined the required outlet air temperature and blower air volume in accordance with the calculation formula that has been obtained based on information received from the sensors. However, because the senses of a person are rather complex, a given temperature is sensed differently, depending on the environment in which the person is situated. For example, a given amount of solar radiation can feel comfortably warm in a cold climate, or extremely uncomfortable in a hot climate. Therefore, as a technique for effecting a higher level of control, a neural network has been adopted in the automatic air conditioning system. With this technique, the data that has been collected under varying environmental conditions is stored in the A/C amplifier. The A/C amplifier can then effect control to provide enhanced air conditioning comfort. The neural network control consists of neurons in the input layer, intermediate layer, and output layer. The input layer neurons process the input data of the outside temperature, the amount of sunlight, and the room temperature based on the outputs of the switches and sensors, and output them to the intermediate layer neurons. Based on this data, the intermediate layer neurons adjust the strength of the links among the neurons. The sum of these is then calculated by the output layer neurons in the form of the required outlet temperature, solar correction, target airflow volume, and outlet mode control volume. Accordingly, the A/C amplifier controls the servo motors and blower motor in accordance with the control volumes that have been calculated by the neural network control.
3. AUTOMATIC RECIRCULATION CONTROL When the automatic recirculation control is operating, the A/C amplifier automatically changes the air inlet mode to fresh air or recirculation air mode based on signals from the smog ventilation sensor, ambient temperature, and room temperature sensors when AUTO air inlet mode is selected. The A/C amplifier detects harmful elements (CO, HC, and NOx) based on smog ventilation sensor signals and automatically switches the air inlet mode to recirculation air mode to prevent such harmful elements from entering the cabin. The A/C amplifier detects cabin temperature based on the room temperature sensor signal and automatically switches the air inlet mode to recirculation air mode to prevent the cabin temperature from becoming too high. The A/C amplifier detects the outside temperature based on the ambient temperature sensor signal and automatically switches the air inlet mode to fresh air mode to prevent the windshield from fogging up.
4. MICRO DUST AND POLLEN FILTER MODE CONTROL When the micro dust and pollen filter switch is pressed, the micro dust and pollen filter mode control is activated. Then, the air vent is switched to the face mode and recirculated pollen free air flows in the area around the upper part of the bodies of the driver and front passenger. When the micro dust and pollen filter switch signal is input to the A/C amplifier, the A/C amplifier controls the A/C compressor, air inlet control servo motor, air outlet control servo motor and blower motor as shown in the timing chart. This control usually operates for approximately 3 minutes. However, when the outside temperature is low, it will operate for approximately 1 minute. After this control stops operating, the A/C amplifier controls the air conditioning system using the AUTO mode.
5. GLOW PLUG CONTROL When the glow plug control is operating, the A/C amplifier and ECM operate two glow plugs to reduce the period of increased fuel consumption due to a cold engine and to improve heater performance. The A/C amplifier and ECM control this function. The A/C amplifier and ECM determine the number of glow plugs to operate based on the engine coolant temperature, outside temperature, and A/C Max. Hot state signals. The A/C amplifier then transmits request signals to the ECM. Based on the request signals from the A/C amplifier and a voltage generation rate signal from the generator, the ECM transmits a glow plug operation permission signal to the A/C amplifier.
6. MODE POSITION AND DAMPER OPERATION Mode Position and Damper Operation FUNCTIONS OF MAIN DAMPERS: Control Damper Operation Position Damper Position Operation Air Inlet Control Damper FRESH A Allows fresh air to enter. RECIRCULATION B Causes internal air to recirculate. Air Mix Control Damper MAX COLD to MAX HOT Temperature Setting C - D - E (C' - D' - E') Varies the mixture ratio of the hot air and the cold air in order to regulate the temperature continuously between hot and cold. Air Outlet Control Damper DEF F, V, L, W, S Defrosts the windshield through the center defroster, side defrosters, side registers, and rear center register. FOOT / DEF G, K, L, P, Q Defrosts the windshield through the center defroster, side defrosters, side registers, and rear center register, while air is also blown out from the front and rear footwell register ducts. FOOT H, K, L, P, Q Air blows out of the front and rear footwell register ducts and side registers. In addition, a small amount of air will blow out from the center defroster and side defrosters. BI-LEVEL I, T, N, U, R Air blows out of the front and rear center registers, side registers and front and rear footwell register ducts. FACE I, J, M, O, S Air blows out of the front and rear center registers and side registers.
7. AIR OUTLETS AND AIRFLOW VOLUME Air Outlets and Airflow Volume The size of the circle o indicates the proportion of airflow volume. *1: Greater airflow volume at the upper area *2: Greater airflow volume at the lower area *3: Greater airflow volume at the defroster *4: Greater airflow volume at the rear *5: Greater airflow volume at the front
8. EVAPORATOR TEMPERATURE SENSOR The evaporator temperature sensor detects the temperature of the cool air immediately past the evaporator in the form of resistance changes, and outputs it to the A/C amplifier.
9. BLOWER MOTOR The blower motor has a built-in blower controller, and is controlled using duty control performed by the A/C amplifier.
10. BUS CONNECTOR Bus connectors are used in the wire harness connection that connects the servo motors to the A/C amplifier. Each bus connector has a built-in communication/driver IC which communicates with the servo motor connector, actuates the servo motor, and has a position detection function. This enables bus communication for the servo motor wire harness, for a more lightweight construction and a reduced number of wires.
11. SERVO MOTOR A pulse pattern type servo motor consists of a printed circuit board and a servo motor. The printed circuit board has three contact points, and can transmit two ON-OFF signals to the A/C amplifier based on the difference of the pulse phases. The bus connector can detect the damper position and movement direction with these signals.
12. COMPRESSOR LOCK SENSOR The compressor lock sensor sends an A/C pulley speed signal to the ECM. The ECM compares this signal with an engine speed signal sent from the crankshaft position sensor. If the ECM determines that the A/C pulley has locked, the ECM turns the magnetic clutch off.
13. ROOM TEMPERATURE SENSOR The room temperature sensor detects the cabin temperature based on changes in the resistance of its built-in thermistor and sends a signal to the A/C amplifier.
14. AMBIENT TEMPERATURE SENSOR The ambient temperature sensor detects the outside temperature based on changes in the resistance of its built-in thermistor and sends a signal to the A/C amplifier.
15. SOLAR SENSOR The solar sensor consists of a photo diode, two amplifier circuits for the solar sensor, and frequency converter circuit for the light control sensor. A solar sensor detects (in the form of changes in the current that flows through the built-in photo diode) the changes in the amount of sunlight from the LH and RH sides (2 directions) and outputs these sunlight strength signals to the A/C amplifier.
16. A/C PRESSURE SENSOR The A/C pressure sensor detects the refrigerant pressure and outputs it to the A/C amplifier in the form of voltage changes.
17. SMOG VENTILATION SENSOR The smog ventilation sensor detects harmful elements such as CO, HC, and NOx, which are present in the air outside of the vehicle. The sensor outputs it to the A/C amplifier. The sensitivity of the smog ventilation sensor can be adjusted. Adjustment can be done using the heater control panel or display and navigation module display.

See also:
• ON-VEHICLE INSPECTION [08/2012 - ]