A/c-Heater System - Automatic: Other Lexus LS II

HEATER VALVE CABLE

Disconnect heater valve cable. Turn ignition on. Press A/C button. Set temperature control knob to maximum cool position. Set heater valve to maximum cool position. (Scheme 16) Install control cable, then secure it with clamp.

Scheme 16

RETRIEVING CODES

1. Simultaneously press and hold AUTO and recirculated air buttons. see scheme 2 Turn ignition on. All indicators will flash 4 times, at one-second intervals. Tone will sound when indicators flash. Press OFF button to cancel indicator check.
2. After indicator check is complete, system will enter self-diagnostic mode. Stored trouble codes will appear in sequence on temperature display panel. See «DIAGNOSTIC CODE IDENTIFICATION»(ref-125187-S21866157732001100400000) table.
3. To slow rate at which codes are displayed, press TEMP (up arrow) switch to change display to step operation. Each time TEMP (up arrow) switch is pressed, display changes by one step.
4. If tone sounds as a code is displayed, problem currently exists. If tone does not sound while code is displayed, problem does not currently exist (history code). Press OFF button to exit self-diagnostics.

DIAGNOSTIC CODE IDENTIFICATION

CLEARING CODES

Remove FUEL OPEN fuse. (Scheme 17) Wait at least 60 seconds before installing fuse. Perform RETRIEVING CODES procedure. Verify only Code 00 is displayed.

Scheme 17

ACTUATOR CHECK

1. Perform step 1) of RETRIEVING CODES procedure. When system enters self-diagnostic mode, press recirculated air button. Each mode door, motor, and relay will operate at one-second intervals. Press TEMP (up arrow) button to display codes one at a time and to step through checks one at a time. Perform step-by-step actuator check.
2. Check airflow and temperature by hand. Tone will sound each time display code changes. Each display code is associated with a system operating condition. (Scheme 18) Press OFF button to cancel actuator check mode.

Scheme 18

CODE 11 - IN-VEHICLE TEMPERATURE SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-2 (Blue wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19)
3. Measure voltage while heating in-vehicle temperature sensor. See «IN-VEHICLE TEMPERATURE SENSOR CIRCUIT SPECIFICATIONS»(ref-125187-S27170817792001100400000) table. IN-VEHICLE TEMPERATURE SENSOR CIRCUIT SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 77 (25) 1.8-2.2 104 (40) 1.2-1.6 (1) As temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest the system. If voltage does not measure as specified, test the in-vehicle sensor. Refer to the «IN-VEHICLE TEMPERATURE SENSOR TEST»(ref-125187-S26755678812001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

Scheme 19

CODE 12 - AMBIENT TEMPERATURE SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-3 (Blue/White wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19)
3. Measure voltage while heating ambient temperature sensor, located behind grille, on lower right side. See «AMBIENT TEMPERATURE»(ref-125187-S03265565892001100400000) SENSOR CIRCUIT SPECIFICATIONS table. AMBIENT TEMPERATURE SENSOR CIRCUIT SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 77 (25) 1.35-1.75 104 (40) 0.85-1.25 (1) As temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test ambient temperature sensor. Refer to the «AMBIENT TEMPERATURE SENSOR TEST»(ref-125187-S14979115262001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 13 - EVAPORATOR TEMPERATURE SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-4 (Yellow/Red wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 21)
3. Measure the voltage at specified temperatures. See «EVAPORATOR TEMPERATURE SENSOR CIRCUIT SPECIFICATIONS»(ref-125187-S18775847802001100400000) table. EVAPORATOR TEMPERATURE SENSOR CIRCUIT SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 32 (0) 2.0-2.4 59 (15) 1.4-1.8 (1) As temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test the evaporator temperature sensor. See the «EVAPORATOR TEMPERATURE SENSOR TEST»(ref-125187-S06348556232001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 14 - COOLANT TEMPERATURE SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Using a digital oscilloscope, measure voltage between terminals A20-6 (Violet wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19) Measure voltage at specified temperatures. (Scheme 20) Compare waveform patterns.
3. If voltage is not as specified, replace coolant temperature sensor. If voltage is as specified, inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

Scheme 20

CODE 15 - DRIVER'S AIR DUCT SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-9 (Gray/Red wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19) Measure voltage at specified conditions. See DRIVER'S AIR DUCT SENSOR CIRCUIT SPECIFICATIONS table. DRIVER'S AIR DUCT SENSOR CIRCUIT SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 32 (0) 1.95-2.05 122 (50) 0.95-1.15 (1) As temperature increases, voltage should gradually decrease.
3. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test driver's air duct sensor. See «DUCT SENSORS TEST»(ref-125187-S20066825582001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 16 - PASSENGER'S AIR DUCT SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-10 (Gray/Blue wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19) Measure the voltage at specified conditions. See «PASSENGER'S AIR DUCT SENSOR CIRCUIT SPECIFICATIONS»(ref-125187-S17745475282001100400000) table. PASSENGER'S AIR DUCT SENSOR CIRCUIT SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 32 (0) 1.95-2.05 122 (50) 0.95-1.15 (1) As temperature increases, voltage should gradually decrease.
3. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage does not measure as specified, test passenger's air duct sensor. Refer to the «DUCT SENSORS TEST»(ref-125187-S20066825582001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 21 - PASSENGER'S SOLAR SENSOR CIRCUIT

Note. If testing is done in a dark area, Code 21 may occur even though system is normal. Shine a light at solar sensor and recheck for Code 21.

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-7 (Gray/Red wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19) Measure the voltage at specified conditions. See «PASSENGER'S SOLAR SENSOR CIRCUIT SPECIFICATIONS»(ref-125187-S29520567432001100400000) table. PASSENGER'S SOLAR SENSOR CIRCUIT SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Less Than 1.0 Sensor Covered By Cloth Greater Than 1.0 (1) As light intensity decreases, voltage should increase.
3. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test solar sensor. See «SOLAR SENSOR»(ref-125187-S02119621262001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 22 - COMPRESSOR LOCK SENSOR CIRCUIT

Note. If installing new belt, set belt tension in range "B" on tensioner scale. (Scheme 21)

1. Reinstall drive belt, and ensure it fits properly on compressor pulley. If tension is not in range "A" on scale, replace belt. (Scheme 21) If tension is okay, go to next step.
2. Start engine. Turn blower and A/C on. Observe compressor. If compressor locks during operation, repair compressor. If compressor does not lock during operation, test compressor lock sensor. See «COMPRESSOR LOCK SENSOR»(ref-125187-S27906422102001100400000) under TESTING. Replace sensor as necessary.
3. If compressor lock sensor is okay, inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

Scheme 21

CODE 23 - PRESSURE SWITCH CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY R & I»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Install manifold gauge set. Turn ignition on.
2. Backprobe A/C-heater control assembly connector between terminal A18-1 (Blue/Black wire) and ground. (Scheme 19)
3. Start engine. Turn blower and A/C on. Battery voltage should exist with low side pressure less than 28 psi (2.0 kg/cm 2 ). If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system.
4. If voltage is not as specified, test pressure switch. See «PRESSURE SWITCH TEST»(ref-125187-S10542816872001100400000) under TESTING. Replace pressure switch as necessary. If switch is okay, go to next step.
5. Inspect wiring harness and connectors between pressure switch and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 24 - DRIVER'S SOLAR SENSOR CIRCUIT

Note. If testing is done in a dark area, Code 24 may occur even though system is normal. Shine a light at solar sensor, and recheck for Code 24.

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn 6ignition on.
2. Backprobe between terminals A19-6 (White wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19) Measure voltage at specified conditions. See DRIVER'S SOLAR SENSOR CIRCUIT SPECIFICATIONS table. DRIVER'S SOLAR SENSOR CIRCUIT SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Less Than 1.0 Sensor Covered By Cloth Greater Than 1.0 (1) As light intensity decreases, voltage should increase.
3. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test solar sensor. See «SOLAR SENSOR»(ref-125187-S02119621262001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 32 OR 42 - AIR INLET DOOR POSITION SENSOR CIRCUIT

Note. For Code 42, see CODE 42 - AIR INLET DOOR SERVOMOTOR CIRCUIT for additional trouble shooting information.

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe between terminals A19-8 (Red/White wire) and A19-16 (Yellow/Green wire) of A/C-heater control assembly connector. (Scheme 19)
3. Measure sensor circuit voltage while pressing buttons to cycle between fresh and recirculated air to activate air inlet door. See «AIR INLET DOOR POSITION SENSOR CIRCUIT SPECIFICATIONS»(ref-125187-S31452787102001100400000) table. AIR INLET DOOR POSITION SENSOR CIRCUIT SPECIFICATIONS Switch/Inlet Position (1) Volts Recirculated Air 3.5-4.5 Fresh Air 0.5-1.8 (1) Voltage should gradually decrease as air inlet door changes from recirculated air to fresh air position.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test air inlet door position sensor. See «AIR INLET»(ref-125187-S40397765852001100400000) DOOR POSITION SENSOR under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between air inlet door servomotor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 34 - DRIVER'S MAXIMUM COOL DOOR POSITION SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C-heater control assembly connector between terminals A19-11 (Violet/Green wire) and A19-16 (Yellow/Green wire). (Scheme 19)
3. Measure sensor circuit voltage while pressing up arrow and then down arrow on TEMP button to change set temperature. As servomotor operates, observe voltmeter. See «DRIVER'S MAXIMUM COOL DOOR»(ref-125187-S23802025572001100400000) POSITION SENSOR CIRCUIT SPECIFICATIONS table. DRIVER'S MAXIMUM COOL DOOR POSITION SENSOR CIRCUIT SPECIFICATIONS Set Temperature (1) Volts Maximum Cool 3.5-4.5 Maximum Hot 0.5-1.8 (1) As set temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test maximum cool door position sensor. See «MAXIMUM COOL DOOR POSITION SENSOR»(ref-125187-S09224613502001100400000) under TESTING. If maximum cool door position sensor is defective, replace maximum cool door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between servomotor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 35 - PASSENGER'S MAXIMUM COOL DOOR POSITION SENSOR CIRCUIT

1. Remove A/C-heater control assembly, leaving harness connectors attached. See «A/C-HEATER CONTROL ASSEMBLY»(ref-125187-S19345710212001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C-heater control assembly connector between terminals A19-12 (Red/Black wire) and A19-16 (Yellow/Green wire). (Scheme 19)
3. Measure sensor circuit voltage while pressing up arrow and then down arrow on TEMP button to change set temperature. As servomotor operates, observe voltmeter. See «PASSENGER'S MAXIMUM COOL»(ref-125187-S28715048212001100400000) DOOR POSITION SENSOR CIRCUIT SPECIFICATIONS table. PASSENGER'S MAXIMUM COOL DOOR POSITION SENSOR CIRCUIT SPECIFICATIONS Set Temperature (1) Volts Maximum Cool 3.5-4.5 Maximum Hot 0.5-1.8 (1) As set temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute known-good A/C-heater control assembly, then retest system. If voltage is not as specified, test maximum cool door position sensor. See «MAXIMUM»(ref-125187-S09224613502001100400000) COOL DOOR POSITION SENSOR under TESTING. If maximum cool door position sensor is defective, replace maximum cool door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between servomotor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute known-good A/C-heater control assembly. Retest system.

CODE 42 - AIR INLET DOOR SERVOMOTOR CIRCUIT

Note. See CODE 32 OR 42 - AIR INLET DOOR POSITION SENSOR CIRCUIT additional trouble shooting information.

1. Warm engine to normal operating temperature. Perform RETRIEVING CODES procedure. After system enters self-diagnostic mode, perform ACTUATOR CHECK. Press TEMP (up arrow) button to enter step mode and display codes. See appropriate AIR INLET DOOR AIRFLOW table. Air inlet door operation should be as specified.
2. If air inlet door functions as specified, no problem is indicated at this time. If air inlet door does not function as specified, test air inlet door servomotor. See «AIR INLET DOOR SERVOMOTOR»(ref-125187-S39913348132001100400000) under TESTING. Replace air inlet door servomotor as necessary. If servomotor is okay, go to next step.
3. Inspect wiring harness and connectors between servomotor and A/C-heater control assembly. Repair as necessary. If wiring harness and connectors are okay, substitute known-good A/C-heater control assembly. Retest system.

AIR INLET DOOR AIRFLOW

Coolant Temperature Switch Check

1. Remove coolant temperature switch, located at lower left side of radiator. Place switch and thermometer in water. Heat water. Check continuity between coolant temperature switch terminals.
2. Continuity should exist when water temperature is less than 181°F (83°C). Continuity should not exist when water temperature is greater than 199°F (93°C). Replace switch if continuity is not as specified.

Cooling Fan Relay Check

Remove left headlight. Remove cooling fan relays. Check continuity between relay terminals. Continuity should exist between terminals No. 1 and 2, and between terminals No. 3 and 4. see scheme 14 Apply battery voltage to relay terminal No. 3. Ground relay terminal No. 4. Continuity should no longer exist between terminals No. 1 and 2. Replace relay(s) if continuity is not as specified.

Driver's Side

1. Remove glove box. Unplug solar sensor harness connector. Cover sensor with cloth. Connect ohmmeter positive lead to White wire terminal, and negative lead to Blue wire terminal of solar sensor. Measure and record resistance between sensor terminals.
2. Remove cloth. Subject sensor to bright light. Again measure resistance between sensor terminals. See «SOLAR SENSOR»(ref-125187-S30208045882001100400000) SPECIFICATIONS table. If resistance is not as specified, replace sensor.

Passenger's Side

1. Remove glove box. Unplug solar sensor harness connector. Cover sensor with cloth. Connect ohmmeter positive lead to Green/Red wire terminal of solar sensor, and connect ohmmeter negative lead to Blue wire terminal. Record sensor resistance.
2. Remove cloth. Subject sensor to bright light, and measure resistance between sensor terminals. If resistance is not as specified, replace sensor. See «SOLAR SENSOR SPECIFICATIONS»(ref-125187-S30208045882001100400000) table.

SOLAR SENSOR SPECIFICATIONS