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Air Conditioning System (Diagnostic Codes & Circuit Tests): Overview Lexus IS III

Automatic HVAC System 22 illustrations ~2499 words

DESCRIPTION

The air conditioning control assembly communicates with the air conditioning amplifier assembly via LIN communication.

If the LIN communication system malfunctions, the air conditioning amplifier assembly does not operate even if the air conditioning control assembly is operated.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B14B2Lost Communication with Front Panel LINLost communication with air conditioning control assemblyHarness or connector between air conditioning control assembly and IG power source Harness or connector between air conditioning control assembly and body ground LIN communication system Air conditioning control assembly Air conditioning amplifier assemblyMemorized (10 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 102

Scheme 102: WIRING DIAGRAM

This DTC is stored if the amount of refrigerant in the air conditioning system is insufficient.

The air conditioning amplifier assembly receives the ambient temperature signal, refrigerant pressure signal, etc. from various sensors.

Based on these signals, the air conditioning amplifier assembly detects the amount of refrigerant.

The A/C switch indicator is turned off and the air conditioning system is stopped if the amount of refrigerant is insufficient.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B14B8Refrigerant ShortageWhen following condition is detected in refrigerant shortage check in normal operation: Amount of refrigerant is insufficientRefrigerant pipe line Cooler expansion valve Air conditioning amplifier assemblyMemorized (15 min. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.
DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
U0100Lost Communication with ECMNo communication with ECMCAN communication system ECMMemorized
U0131Lost Communication with Electric Power Steering ECUNo communication with power steering ECU assemblyCAN communication system Power steering ECU assemblyMemorized
U0142Lost Communication with Main Body ECUNo communication with main body ECU (multiplex network body ECU)CAN communication system Main body ECU (multiplex network body ECU)Memorized
U0151Lost Communication with Restraints Control ModuleNo communication with airbag sensor assemblyCAN communication system Airbag sensor assemblyMemorized
U0155Lost Communication with Combination MeterNo communication with combination meter assemblyCAN communication system Combination meter assemblyMemorized
U0163Lost Communication with Navigation Control ModuleNo communication with radio receiver assemblyCAN communication system Radio receiver assemblyMemorized

In this circuit, the cooler compressor assembly (compressor solenoid) receives a refrigerant compression demand signal from the air conditioning amplifier assembly.

Based on this signal, the cooler compressor assembly (compressor solenoid) changes the amount of compressor output.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1451/51Compressor Solenoid CircuitOpen or short in compressor solenoid circuitCooler compressor assembly (compressor solenoid) Harness or connector between air conditioning amplifier assembly and cooler compressor assembly (compressor solenoid) Air conditioning amplifier assembly

Scheme 103

Scheme 103: WIRING DIAGRAM

The No. 2 air conditioning radiator damper servo sub-assembly (driver side upper air mix) sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 2 air conditioning radiator damper servo sub-assembly (driver side upper air mix) to the appropriate position. As a result, the amount of air passing through the heater core after passing through the evaporator is adjusted, and the temperature of the air blowing toward the driver seat side is controlled.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1446/46Air Mix Damper Control Servo Motor Circuit (Driver Side)Air mix damper position sensor value does not change even if air conditioning amplifier assembly operates No. 2 air conditioning radiator damper servo sub-assembly (driver side upper air mix)No. 2 air conditioning radiator damper servo sub-assembly (driver side upper air mix) Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 104

Scheme 104: WIRING DIAGRAM

The No. 3 air conditioning radiator damper servo sub-assembly sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 3 air conditioning radiator damper servo sub-assembly to the appropriate position, which controls the air outlet switching.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1443/43Air Outlet Damper Control Servo Motor CircuitAir outlet damper position sensor value does not change even if air conditioning amplifier assembly operates No. 3 air conditioning radiator damper servo sub-assemblyNo. 3 air conditioning radiator damper servo sub-assembly Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 105

Scheme 105: WIRING DIAGRAM

The No. 1 blower damper servo sub-assembly sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the air inlet mode selection No. 1 blower damper servo sub-assembly to the appropriate position, which controls the air inlet mode (fresh, recirculation/fresh, and recirculation).

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1442/42Air Inlet Damper Control Servo Motor CircuitAir inlet damper position sensor value does not change even if air conditioning amplifier assembly operates No. 1 blower damper servo sub-assemblyNo. 1 blower damper servo sub-assembly Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 106

Scheme 106: WIRING DIAGRAM

The air conditioning harness assembly connects the air conditioning amplifier assembly and the servo motors. The air conditioning amplifier assembly supplies power and sends operation instructions to each servo motor through the air conditioning harness assembly. Each servo motor sends damper position information to the air conditioning amplifier assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1497/97BUS IC Communication MalfunctionError or open in communication lineAir conditioning harness assembly No. 1 air conditioning radiator damper servo sub-assembly No. 2 air conditioning radiator damper servo sub-assembly (driver side upper air mix) No. 2 air conditioning radiator damper servo sub-assembly (front passenger side upper air mix) No. 5 air conditioning radiator damper servo sub-assembly (driver side lower air mix) No. 4 air conditioning radiator damper servo sub-assembly (front passenger side lower air mix) No. 3 air conditioning radiator damper servo sub-assembly No. 1 blower damper servo sub-assembly Air conditioning amplifier assemblyMemorized (10 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 107

Scheme 107: WIRING DIAGRAM

The No. 5 air conditioning radiator damper servo sub-assembly (driver side lower air mix) sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 5 air conditioning radiator damper servo sub-assembly (driver side lower air mix) to the appropriate position. As a result, the amount of air passing through the heater core after passing through the evaporator is adjusted, and the temperature of the air blowing toward the driver seat side is controlled.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1453/53Driver Side Air Outlet Damper COOL Control Servo Motor CircuitAir mix damper position sensor value does not change even if air conditioning amplifier assembly operates No. 5 air conditioning radiator damper servo sub-assembly (driver side lower air mix)No. 5 air conditioning radiator damper servo sub-assembly (driver side lower air mix) Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 108

Scheme 108: WIRING DIAGRAM

The No. 4 air conditioning radiator damper servo sub-assembly (front passenger side lower air mix) sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 4 air conditioning radiator damper servo sub-assembly (front passenger side lower air mix) to the appropriate position. As a result, the amount of air passing through the heater core after passing the evaporator is adjusted, and the temperature of the air blowing toward the passenger seat side is controlled. The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1454/54Passenger Side Air Outlet Damper COOL Control Servo Motor CircuitAir mix damper position sensor value does not change even if air conditioning amplifier assembly operates No. 4 air conditioning radiator damper servo sub-assembly (front passenger side lower air mix)No. 4 air conditioning radiator damper servo sub-assembly (front passenger side lower air mix) Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 109

Scheme 109: WIRING DIAGRAM

The No. 1 air conditioning radiator damper servo sub-assembly sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 1 air conditioning radiator damper servo sub-assembly to the appropriate position, which controls the air outlet switching.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1455/55Driver Side Air Outlet Damper FOOT/DEF Control Servo Motor CircuitAir outlet damper position sensor value does not change even if air conditioning amplifier assembly operates No. 1 air conditioning radiator damper servo sub-assemblyNo. 1 air conditioning radiator damper servo sub-assembly Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 110

Scheme 110: WIRING DIAGRAM

The cooler (room temp. sensor) thermistor is installed in the instrument panel to detect the cabin temperature, which is used to control the air conditioning system. The resistance of the cooler (room temp. sensor) thermistor changes in accordance with the cabin temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the cooler (room temp. sensor) thermistor and reads voltage changes due to changes in the resistance of the cooler (room temp. sensor) thermistor.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1411/11Room Temperature Sensor CircuitOpen or short in room temperature sensor circuitCooler (room temp. sensor) thermistor Harness or connector between cooler (room temp. sensor) thermistor and air conditioning amplifier assembly Air conditioning amplifier assemblyMemorized (4 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

HINT

If the cabin temperature is approximately -18.6°C (-1.48°F) or lower, DTC B1411/11 may be output even though the system is normal.

Scheme 111

Scheme 111: WIRING DIAGRAM

Scheme 112

Scheme 112: PROCEDURE
  1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data List. Check the value(s) by referring to the table below. Body Electrical > Air Conditioner > Data List Tester Display Measurement Item Range Normal Condition Diagnostic Note Room Temperature Sensor Cooler (room temp. sensor) thermistor Min.: -6.50°C (20.30°F) Max.: 57.25°C (135.05°F) Actual cabin temperature displayed - Body Electrical > Air Conditioner > Data List Tester Display Room Temperature Sensor OK The display is as specified in the normal condition column. Result Result Proceed to NG A OK (When troubleshooting according to Problem Symptoms Table) B OK (When troubleshooting according to the DTC) C Result: 2 B PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE [04/2013 - ]»(ref-665545-S02258281842014102400000) Result: 3 C REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL [04/2013 - ]»(ref-665718-S03696019692014102400000) Result: 1 A See step 2
  2. INSPECT COOLER (ROOM TEMP. SENSOR) THERMISTOR Remove the cooler (room temp. sensor) thermistor. *a Component without harness connected (Cooler (Room Temp. Sensor) Thermistor) *b Sensing Portion *c Resistance (kohms) *d Temperature (°C (°F)) *e Allowable Range Refer to «REMOVAL [04/2013 - ]»(ref-665718-S17194674972014102400000) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition 1 - 2 10°C (50°F) 3.00 to 3.73 kohms 15°C (59°F) 2.45 to 2.88 kohms 20°C (68°F) 1.95 to 2.30 kohms 25°C (77°F) 1.60 to 1.80 kohms 30°C (86°F) 1.28 to 1.47 kohms 35°C (95°F) 1.00 to 1.22 kohms 40°C (104°F) 0.80 to 1.00 kohms 45°C (113°F) 0.65 to 0.85 kohms 50°C (122°F) 0.50 to 0.70 kohms 55°C (131°F) 0.44 to 0.60 kohms 60°C (140°F) 0.36 to 0.50 kohms NOTE: Hold the sensor only by its connector. Touching the sensing portion may change the resistance value. When measuring, the sensor temperature must be the same as the ambient temperature. HINT: As the temperature increases, the resistance decreases (see the graph). Result Proceed to OK NG Result: 2 NG REPLACE COOLER (ROOM TEMP. SENSOR) THERMISTOR. Refer to «REMOVAL [04/2013 - ]»(ref-665718-S17194674972014102400000) Result: 1 OK See step 3
  3. CHECK HARNESS AND CONNECTOR (COOLER (ROOM TEMP. SENSOR) THERMISTOR - AIR CONDITIONING AMPLIFIER ASSEMBLY) Disconnect the K11 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition K11-16 (TR) - K86-1 Always Below 1 ohms K11-1 (SG-1) - K86-2 Always Below 1 ohms K11-16 (TR) - Body ground Always 10 kohms or higher K11-1 (SG-1) - Body ground Always 10 kohms or higher Result Proceed to OK NG Result: 1 OK REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL [04/2013 - ]»(ref-665718-S03696019692014102400000) Result: 2 NG REPAIR OR REPLACE HARNESS OR CONNECTOR

The thermistor assembly is installed in front of the cooler condenser assembly to detect the ambient temperature, which is used to control the air conditioning system. This sensor is connected to the air conditioning amplifier assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the air conditioning amplifier assembly. The resistance of the thermistor assembly changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the thermistor assembly and reads voltage changes due to changes in the resistance of the thermistor assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1412/12Ambient Temperature Sensor CircuitOpen or short in ambient temperature sensor circuitThermistor assembly Harness or connector between thermistor assembly and air conditioning amplifier assembly Air conditioning amplifier assemblyMemorized (4 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

HINT

If the ambient temperature is approximately -52.9°C (-63.22°F) or lower, DTC B1412/12 may be output even though the system is normal.

Scheme 113

Scheme 113: WIRING DIAGRAM

The No. 1 cooler thermistor is installed on the evaporator in the air conditioner unit to detect the temperature of the cooled air that has passed through the evaporator, which is used to control the air conditioning system. It sends signals to the air conditioning amplifier assembly. The resistance of the No. 1 cooler thermistor changes in accordance with the temperature of the cooled air that has passed through the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the No. 1 cooler thermistor and reads voltage changes as the resistance of the No. 1 cooler thermistor changes. This sensor is used for frost prevention.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1413/13Evaporator Temperature Sensor CircuitOpen or short in evaporator temperature sensor circuitNo. 1 cooler thermistor Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (4 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 114

Scheme 114: WIRING DIAGRAM

The ECM sends the engine speed signal to the air conditioning amplifier assembly via CAN communication.

The air conditioning amplifier assembly reads the difference between compressor speed and engine speed. When the difference becomes too large, the air conditioning amplifier assembly determines that the compressor is locked, and turns the magnetic clutch assembly off.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1422/22Compressor Lock Sensor CircuitOpen or short in A/C lock sensor circuitMagnetic clutch assembly Cooler compressor assembly Harness or connector between cooler compressor assembly and air conditioning amplifier assembly Air conditioning amplifier assemblyMemorized (3 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 115

Scheme 115: WIRING DIAGRAM

This DTC is stored if refrigerant pressure on the high pressure side is extremely low (176 kPa (1.8 kgf/cm 2 , 26 psi) or less) or extremely high (3025 kPa (30.8 kgf/cm 2 , 439 psi) or more). The air conditioner pressure sensor, which is installed on the high pressure side pipe to detect refrigerant pressure, sends a refrigerant pressure signal to the air conditioning amplifier assembly. The air conditioning amplifier assembly converts this signal to a pressure value according to the sensor characteristics and uses it to control the compressor.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1423/23Pressure Sensor CircuitOpen or short in air conditioner pressure sensor circuit Refrigerant pressure on high pressure side is extremely low (176 kPa (1.8 kgf/cm 2 , 26 psi) or less) or extremely high (3025 kPa (30.8 kgf/cm 2 , 439 psi) or more)Air conditioner pressure sensor Harness or connector between air conditioner pressure sensor and air conditioning amplifier assembly Air conditioning amplifier assembly Cooler expansion valve (blocked, stuck) Cooler condenser assembly (blocked, deterioration of cooling capacity due to dirt) Cooler dryer (moisture in the refrigerant cycle cannot be absorbed) Cooling fan system (cooler condenser assembly cannot be cooled down) Air conditioning system (leaks, blocked)

Scheme 116

Scheme 116: WIRING DIAGRAM

The No. 2 air conditioning radiator damper servo sub-assembly (front passenger side upper air mix) sends pulse signals to inform the air conditioning amplifier assembly of the damper position. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the No. 2 air conditioning radiator damper servo sub-assembly (front passenger side upper air mix) to the appropriate position. This adjusts the amount of air passing through the heater core after passing the evaporator and controls the temperature of the output air. The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMemory
B1441/41Air Mix Damper Control Servo Motor Circuit (Passenger Side)Air mix damper position sensor value does not change even if air conditioning amplifier assembly operates No. 2 air conditioning radiator damper servo sub-assembly (front passenger side upper air mix)No. 2 air conditioning radiator damper servo sub-assembly (front passenger side upper air mix) Air conditioning harness assembly Air conditioning amplifier assemblyMemorized (30 sec. or more)*1
  1. *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

Scheme 117

Scheme 117: WIRING DIAGRAM

The blower motor with fan sub-assembly is operated by signals from the air conditioning amplifier assembly. Blower motor speed signals are transmitted in accordance with changes in the duty ratio.

Scheme 118

Scheme 118: WIRING DIAGRAM

When the air conditioning amplifier assembly is turned on, a magnetic clutch on signal is sent from the MGC terminal of the air conditioning amplifier assembly. Then, the semiconductor pwr integration ECU turns on to operate the magnetic clutch assembly.

Scheme 119

Scheme 119: WIRING DIAGRAM

The air conditioning amplifier assembly sends operation signals to the PTC heater relays when quick heater assembly operation conditions are met. Based on the signals from the air conditioning amplifier assembly, the PTC heater relays turn on, and power is supplied to the quick heater assembly installed in the air conditioning radiator assembly.

Control ECUCondition
Air Conditioning Amplifier AssemblyEngine running
Combination switch assembly (ECO mode switch) off
Blower switch: on
Temperature settings: MAX HOT
Light control switch assembly off
Engine coolant temperature 69°C (156°F) or lower (2 PTC heater relays operating) Engine coolant temperature 72°C (162°F) or lower (1 PTC heater relay operating)
Ambient temperature 3°C (37°F) or lower

QUICK HEATER ASSEMBLY OPERATION CONDITION

Scheme 120

Scheme 120: WIRING DIAGRAM

When the combination switch assembly (ECO mode switch) is turned on, the air conditioning amplifier assembly receives a combination switch assembly (ECO mode switch) ON signal and controls the air conditioning to enhance fuel efficiency.

Scheme 121

Scheme 121: WIRING DIAGRAM

Power source voltage is supplied to the air conditioning amplifier assembly when the engine switch is turned on (IG). This power is used for operating the air conditioning amplifier assembly, servo motors, etc.

Scheme 122

Scheme 122: WIRING DIAGRAM

The back-up power source circuit for the air conditioning amplifier assembly is shown below. Power is supplied even when the engine switch is off. This power is used for diagnostic trouble code memory, etc.

Scheme 123

Scheme 123: WIRING DIAGRAM