A/c-Heater System: Other Lexus GS II

SYSTEM CONTROLS

The A/C control assembly consists of a liquid crystal display, separate driver and passenger temperature controls, fan speed control, airflow control switches, and various buttons which activate A/C-heater system, direct discharged air to appropriate outlets, and activate front and rear defoggers. (Scheme 5)

Scheme 5

RETRIEVING CODES

1. While pressing and holding AUTO button and recirculated/fresh air button, turn ignition on. Indicators will flash on and off at one-second intervals, 4 times in succession, and a tone will sound as an indicator check. 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 driver's side temperature display. See «AUTOMATIC A/C-HEATER SYSTEM TROUBLE CODES»(ref-125255-S09794399552001100400000) table.
3. Press driver's side temperature switch to display codes one at a time. If tone sounds when code is displayed, problem causing code currently exists. If tone does not sound when code is displayed, associated problem is past history, and does not currently exist. Press OFF button to exit self-diagnostics.

AUTOMATIC A/C-HEATER SYSTEM TROUBLE CODES

CLEARING CODES

Remove ECU-B2 fuse from passenger side junction block for 10 seconds or longer to clear memory. Junction block is located behind passenger side kick panel. After reinstalling fuse, verify only normal code (Code 00) appears.

ACTUATOR CHECK

1. Perform INDICATOR CHECK under «RETRIEVING CODES»(ref-125255-S41262574652001100400000). When system enters self-diagnostic mode, press recirculated/fresh air button. Each mode door, motor, and relay will operate at one-second intervals. Press A/C switch to display codes one at a time and to step through checks one at a time.
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 6) Press OFF button to cancel actuator check mode.

Scheme 6

CODE 11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA13-14 (Red wire) and A13-19 (Black/Yellow wire). (Scheme 7) Measure voltage while heating sensor. See «IN-VEHICLE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-125255-S27882077962001100400000) table. IN-VEHICLE TEMPERATURE SENSOR CIRCUIT VOLTAGE 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.
3. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test in-vehicle temperature sensor. See procedures in «IN-VEHICLE TEMPERATURE SENSOR»(ref-125255-S04878525912001100400000) 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 control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly. Retest system.

Scheme 7

CODE 12: OUTSIDE TEMPERATURE SENSOR CIRCUIT

1. Access Engine Control Module (ECM) located at left front corner of engine compartment. Leave harness connectors attached. (Scheme 8) Turn ignition on.
2. On GS300, backprobe ECM connector terminals E5-10 (Light Green/Red wire) and E3-18 (Brown wire). On GS400, backprobe ECM connector terminals E7-22 (Light Green/Red wire) and E3-18 (Brown wire). On all models, measure voltage while heating outside temperature sensor. See «OUTSIDE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-125255-S21605911642001100400000) table. OUTSIDE TEMPERATURE SENSOR CIRCUIT VOLTAGE 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.
3. If voltage is as specified, temporarily substitute a known-good ECM, then retest system. If voltage is not as specified, test outside temperature sensor. See «OUTSIDE TEMPERATURE SENSOR»(ref-125255-S17007758692001100400000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor, ECM and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly. Retest system.

Scheme 8

CODE 13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION.
2. Turn ignition on. Backprobe A/C control assembly connector between terminals A13-2 (Red/Green wire) and A14-13 (Red wire). (Scheme 7)
3. Measure evaporator temperature sensor voltage at specified temperature. See «EVAPORATOR TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-125255-S41693871822001100400000) table. EVAPORATOR TEMPERATURE SENSOR CIRCUIT VOLTAGE 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 a known-good A/C control assembly, then retest system. If voltage is not as specified, test evaporator temperature sensor. See procedures in «EVAPORATOR TEMPERATURE SENSOR TESTING»(ref-125255-S31391975362001100400000). Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 18: EXHAUST GAS SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION.
2. Turn ignition on. Backprobe A/C control assembly connector between terminals A13-3 (Blue/White wire) and A13-15 (Blue/Red wire). (Scheme 7)
3. Voltage should be 1.0-4.5 volts at 50-95°F (10-35°C). When sensor is exposed to exhaust gas, the voltage should decrease. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system.
4. If voltage is not as specified, test exhaust gas sensor. See «EXHAUST GAS SENSOR»(ref-125255-S26490285842001100400000) 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 control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 21: SOLAR SENSOR CIRCUIT (PASSENGER SIDE)

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

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA14-4 (Black/Red wire) and A14-1 (White/Red wire). (Scheme 7) Measure sensor circuit voltage. See «SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-125255-S28734291222001100400000) table. SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Less Than 0.8 Sensor Covered By Cloth 0.8-4.3 (1) As light intensity decreases, voltage should increase.
3. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test solar sensor. See «SOLAR SENSOR»(ref-125255-S25134042162001100400000) 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 control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 22: COMPRESSOR LOCK SENSOR CIRCUIT

1. Access Engine Control Module (ECM) located at left front corner of engine compartment. Leave harness connectors attached. (Scheme 9) Start engine. Press AUTO and A/C buttons to ON position.
2. On GS300, backprobe ECM connector terminal E2-29 (Gray wire) and ground. (Scheme 9) On GS400, backprobe ECM connector terminal E7-21 (Gray wire) and ground. On all models, battery voltage should exist.
3. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, test compressor lock sensor. See «COMPRESSOR LOCK SENSOR»(ref-125255-S34583489962001100400000) under TESTING. If sensor is okay, go to next step. Replace sensor as necessary.
4. Inspect wiring harness and connectors between A/C control assembly, ECM, and A/C compressor lock sensor. Repair harness and connectors as necessary. If wiring harness and connectors are okay, temporarily substitute known-good ECM and/or A/C control assembly, and retest system.

Scheme 9

CODE 23: PRESSURE SWITCH CIRCUIT

1. Access Engine Control Module (ECM) located at left front corner of engine compartment. Leave harness connectors attached. Install manifold gauge set. Turn ignition on.
2. On GS300, backprobe ECM connector between terminal E5-21 (Blue/Black wire) and ground. (Scheme 10) On GS400, backprobe ECM connector between terminal E7-23 (Blue/Black wire) and ground. (Scheme 10)
3. Start engine. Press A/C button to ON position. Battery voltage should exist with refrigerant pressure is greater than 28 psi (2.0 kg/cm 2 ) and less than 455 psi (32 kg/cm 2 ). If voltage is as specified, no problem is indicated at this time.
4. If voltage is not as specified, test pressure switch. See «PRESSURE SWITCH TESTING»(ref-125255-S33472620172001100400000). If switch is okay, go to next step. Replace pressure switch as necessary.
5. Inspect wiring harness and connectors between pressure switch, ECM and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good ECM and/or A/C control assembly, then retest system.

Scheme 10

CODE 24: SOLAR SENSOR CIRCUIT (DRIVER SIDE)

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

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA14-4 (Black/Red wire) and A14-9 (White/Green wire). (Scheme 7) Measure sensor circuit voltage. See SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS table. SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Less Than 0.8 Sensor Covered By Cloth 0.8-4.3 (1) As light intensity decreases, voltage should increase.
3. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test solar sensor. See «SOLAR SENSOR»(ref-125255-S25134042162001100400000) 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 control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 31 OR 41: AIR MIX DOOR POSITION SENSOR CIRCUIT

(PASSENGER SIDE)

Note. For Code 41, see CODE 41: AIR MIX SERVOMOTOR CIRCUIT (PASSENGER SIDE) for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA14-13 (Black wire) and A14-11 (Green/Red wire). (Scheme 7)
3. Measure sensor circuit voltage while changing set temperature to activate air mix door. See «AIR MIX DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S30969293052001100400000) table. AIR MIX DOOR POSITION SENSOR SPECIFICATIONS Set Temperature (1) Volts Maximum Cool 3.5-4.5 Maximum Hot 0.5-1.5 (1) As set temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test air mix door position sensor. See «AIR MIX DOOR POSITION SENSOR»(ref-125255-S13756933072001100400000) under TESTING. If position sensor is defective, replace air mix door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 32 OR 42: AIR INLET DOOR POSITION SENSOR CIRCUIT

Note. For Code 42, see CODE 42: AIR INLET SERVOMOTOR CIRCUIT for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A13-6 (Red/White wire) and A13-18 (Black/Orange wire). (Scheme 7)
3. Measure sensor voltage while pressing recirculation/fresh air button to change air inlet between recirculated and fresh air. As servomotor operates, note voltage. See «AIR INLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S15603227122001100400000) table. AIR INLET DOOR POSITION SENSOR SPECIFICATIONS Position (1) Volts Recirculated Air 3.5-4.5 Fresh Air 0.5-1.5 (1) As door moves from recirculated air position toward fresh air position, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test air inlet door position sensor. See procedures in «AIR INLET DOOR POSITION SENSOR»(ref-125255-S31841123832001100400000) under TESTING. If air inlet door position sensor is defective, replace air inlet door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 33 OR 43: AIR OUTLET DOOR POSITION SENSOR CIRCUIT

Note. For Code 43, see CODE 43: AIR OUTLET SERVOMOTOR CIRCUIT for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A14-3 (Green/Orange wire) and A14-13 (Black wire). (Scheme 7)
3. Measure sensor circuit voltage while rotating airflow control knob from vent to defrost position. As servomotor operates, note voltage. See «AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S40184774462001100400000) table. AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS Position (1) Volts Vent 3.5-4.5 Defrost 0.5-1.5 (1) As door moves from defrost position toward vent position, voltage should gradually increase.
4. If voltage is as specified, temporarily substitute a known-good A/C control assembly, then retest system. If voltage is not as specified, test air outlet door position sensor. See procedures in «AIR OUTLET DOOR POSITION SENSOR»(ref-125255-S02566415052001100400000) under TESTING. If position sensor is okay, go to next step. If air outlet door position sensor is defective, replace air outlet servomotor.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 36 OR 46: AIR MIX DOOR POSITION SENSOR CIRCUIT (DRIVER

SIDE)

Note. For Code 46, see CODE 46: AIR MIX SERVOMOTOR CIRCUIT (DRIVER SIDE) for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA14-10 (White wire) and A14-13 (Black wire). (Scheme 7)
3. Measure sensor circuit voltage while changing set temperature to activate air mix door. See «AIR MIX DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S30969293052001100400000) table. AIR MIX DOOR POSITION SENSOR SPECIFICATIONS Set Temperature (1) Volts Maximum Cool 3.5-4.5 Maximum Hot 0.5-1.5 (1) As set temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known-good A/C control assembly and retest. If voltage is not as specified, test door position sensor. See «AIR MIX DOOR POSITION SENSOR»(ref-125255-S13756933072001100400000) under TESTING. If position sensor is defective, replace air mix door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 41: AIR MIX SERVOMOTOR CIRCUIT (PASSENGER SIDE)

Note. See CODE 31 OR 41: AIR MIX DOOR POSITION SENSOR CIRCUIT (PASSENGER SIDE) for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-125255-S41262574652001100400000) procedure. After system enters self-diagnostic mode, perform ACTUATOR CHECK. Press A/C switch button to enter step mode and display codes. See appropriate AIR MIX DOOR AIRFLOW table. Air mix door operation should be as specified. AIR MIX DOOR AIRFLOW Code Air Mix Door Expected Result 0-3 Fully Closed Cool Air Comes Out 4-5 Half Open Blend (Cool/Hot) Air Comes Out 6-9 Fully Open Hot Air Comes Out
2. If air mix door functions as specified, no problem is indicated at this time. If air mix door does not function as specified, test air mix door servomotor. See «AIR MIX DOOR SERVOMOTOR (PASSENGER SIDE)»(ref-125255-S41352272002001100400000) under TESTING. If position sensor is okay, go to next step. Replace air mix door servomotor as necessary.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 42: AIR INLET SERVOMOTOR CIRCUIT

Note. See CODE 32 OR 42: AIR INLET DOOR POSITION SENSOR CIRCUIT for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-125255-S41262574652001100400000) procedure. After system enters self-diagnostic code check mode, perform ACTUATOR CHECK. Press A/C button to enter step mode and display codes. See appropriate AIR INLET DOOR AIRFLOW table. Air inlet door operation should be as specified. AIR INLET DOOR AIRFLOW Code Door Position 0-1 Fresh Air 2 Fresh/Recirculated Air 3-5 Recirculated Air 6-9 Fresh Air
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 servomotor. See «AIR INLET DOOR SERVOMOTOR»(ref-125255-S15527496762001100400000) under TESTING. Replace air inlet door servomotor as necessary. If air inlet door servomotor is okay, go to next step.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 43: AIR OUTLET SERVOMOTOR CIRCUIT

Note. See CODE 33 OR 43: AIR OUTLET DOOR POSITION SENSOR CIRCUIT for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-125255-S41262574652001100400000) procedure. After system enters self-diagnostic mode, perform ACTUATOR CHECK. Press A/C button to enter step mode and display codes. See appropriate AIR OUTLET DOOR AIRFLOW table. Air outlet door operation should be as specified. AIR OUTLET DOOR AIRFLOW Code Airflow Mode 0-1 Face 2-4 Bi-Level 5-7 Foot 8 Foot/Defrost 9 Defrost
2. If air outlet door servomotor functions as specified, no problem is indicated at this time. If air outlet door does not function as specified, test servomotor. See «AIR OUTLET DOOR SERVOMOTOR»(ref-125255-S15070501222001100400000) under TESTING. Replace servomotor as necessary. If air outlet servomotor is okay, go to next step.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

CODE 46: AIR MIX SERVOMOTOR CIRCUIT (DRIVER SIDE)

Note. See CODE 36 OR 46: AIR MIX DOOR POSITION SENSOR CIRCUIT (DRIVER SIDE) for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-125255-S41262574652001100400000) procedure. After system enters self-diagnostic mode, perform ACTUATOR CHECK. Press A/C switch button to enter step mode and display codes. See appropriate AIR MIX DOOR AIRFLOW table. Air mix door operation should be as specified. AIR MIX DOOR AIRFLOW Code Air Mix Door Expected Result 0-3 Fully Closed Cool Air Comes Out 4-5 Half Open Blend (Cool/Hot) Air Comes Out 6-9 Fully Open Hot Air Comes Out
2. If air mix door functions as specified, no problem is indicated at this time. If air mix door does not function as specified, test air mix door servomotor. See «AIR MIX DOOR SERVOMOTOR (DRIVER SIDE)»(ref-125255-S41352272002001100400000) under TESTING. If position sensor is okay, go to next step. Replace air mix door servomotor as necessary.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C control assembly, then retest system.

ACCESSORY POWER CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on. Backprobe between A/C control assembly connector terminals A13-2 (Gray wire) and A13-22 (White/Black wire). (Scheme 7) If battery voltage is present, no problem is indicated at this time. If battery voltage is not present, go to next step.
2. Backprobe between A/C control assembly connector terminal A13-22 (White/Black wire) and ground. If continuity is present, go to next step. If continuity is not present, repair open in White/Black wire between A/C control assembly connector terminal A13-22 and ground.
3. Inspect RADIO NO. 2 fuse at driver's side interior fuse block. If fuse is blown, correct cause and replace fuse. If fuse is okay, inspect wiring harness and connectors between fuse and A/C control assembly.

AIR INLET DOOR POSITION SENSOR

1. Remove heater core. See «HEATER CORE»(ref-125255-S27080096952001100400000) under REMOVAL & INSTALLATION. Unplug air inlet servomotor connector. Measure resistance between servomotor connector terminals No. 1 and No. 3. (Scheme 11)
2. If resistance is not 4200-7800 ohms, replace air inlet servomotor. If resistance is as specified, go to next step.
3. Connect ohmmeter between servomotor terminals No. 3 (Black/White wire) and No. 5 (Red/Black wire). Apply battery voltage to air inlet servomotor connector terminal No. 2 (Red/White wire). Connect terminal No. 1 (Red/Blue wire) to ground.
4. Measure resistance as servomotor operates. Transpose power leads. Again measure resistance. Resistance should be as specified for each door position. See «AIR INLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S15603227122001100400000) table.

Scheme 11

AIR INLET DOOR POSITION SENSOR SPECIFICATIONS

AIR INLET DOOR SERVOMOTOR

1. Remove cooling unit. See «COOLING UNIT»(ref-125255-S25465348372001100400000) under REMOVAL & INSTALLATION. Unplug air inlet servomotor connector. Connect battery voltage to servomotor terminal No. 6. Connect terminal No. 7 to ground. (Scheme 12)
2. Servomotor lever should move smoothly to recirculation position. Transpose power leads. Servomotor lever should move smoothly to fresh air position. If operation is not as specified, replace servomotor.

Scheme 12

Driver Side

1. Remove heater core. See «HEATER CORE»(ref-125255-S27080096952001100400000) under REMOVAL & INSTALLATION. Unplug air mix servomotor connector. Measure resistance between servomotor connector terminals No. 1 and No. 3. (Scheme 13)
2. If resistance is not 4200-7800 ohms, replace air mix servomotor. If resistance is as specified, go to next step.
3. Connect ohmmeter between servomotor terminals No. 1 and No. 5. Apply battery voltage to air mix servomotor connector terminal No. 6. Connect terminal No. 7 to ground.
4. As servomotor operates, measure resistance. Transpose power leads. Again measure resistance. Resistance should be as specified for each door position. See «AIR MIX DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S30969293052001100400000) table. If resistance is not as specified, replace air mix door servomotor.

AIR MIX DOOR POSITION SENSOR SPECIFICATIONS

Scheme 13

Passenger Side

1. Remove heater unit. See HEATER UNIT under REMOVAL & INSTALLATION. Unplug air mix servomotor connector. Measure resistance between servomotor connector terminals No. 1 and No. 3. (Scheme 14)
2. If resistance is not 4200-7800 ohms, replace air mix servomotor. If resistance is as specified, go to next step.
3. Connect ohmmeter between servomotor terminals No. 1 and No. 5. Apply battery voltage to air mix servomotor connector terminal No. 6. Connect terminal No. 7 to ground.
4. As servomotor operates, measure resistance. Transpose power leads. Again measure resistance. Resistance should be as specified for each door position. See «AIR MIX DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S30969293052001100400000) table. If resistance is not as specified, replace air mix door servomotor.

AIR MIX DOOR POSITION SENSOR SPECIFICATIONS

Scheme 14

1. Remove heater unit. See HEATER UNIT under REMOVAL & INSTALLATION. Unplug air mix servomotor connector. Apply battery voltage to air mix servomotor connector terminal No. 6. Connect terminal No. 7 to ground. (Scheme 15) Servomotor lever should move smoothly to hot side.
2. Transpose power leads. Servomotor lever should move smoothly to cool side. Replace servomotor if it does not function as specified.

Scheme 15

1. Remove heater unit. See HEATER UNIT under REMOVAL & INSTALLATION. Unplug air mix servomotor connector. Apply battery voltage to air mix servomotor connector terminal No. 6. Connect terminal No. 7 to ground. (Scheme 16) Servomotor lever should move smoothly to hot side.
2. Transpose power leads. Servomotor lever should move smoothly to cool side. Replace servomotor if it does not function as specified.

Scheme 16

AIR OUTLET DOOR POSITION SENSOR

1. Remove heater unit. See HEATER UNIT under REMOVAL & INSTALLATION. Unplug air outlet servomotor connector. Measure resistance between servomotor connector terminals No. 1 and No. 3 (Red/Yellow wire). (Scheme 17)
2. If resistance is not 4200-7800 ohms, replace air outlet servomotor. If resistance is as specified, go to next step.
3. Connect ohmmeter between servomotor terminals No. 1 and No. 5. Apply battery voltage to air outlet servomotor connector terminal No. 6. Connect terminal No. 7 to ground. (Scheme 18)
4. Measure resistance as servomotor operates. Transpose power leads. Again measure resistance. Resistance should be as specified for each door position. See «AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-125255-S40184774462001100400000) table.

AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS

Scheme 17

AIR OUTLET DOOR SERVOMOTOR

1. Remove heater unit. See HEATER UNIT under REMOVAL & INSTALLATION. Unplug air outlet servomotor connector. Apply battery voltage to air mix servomotor connector terminal No. 6. Connect terminal No. 7 to ground. (Scheme 18) Servomotor lever should move smoothly to face side.
2. Transpose power leads. Servomotor lever should move smoothly to defrost side. If servomotor lever does not function as specified, replace servomotor.

Scheme 18

BACK-UP POWER CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Backprobe between A/C control assembly connector terminal A13-1 (White/Red wire) and ground. (Scheme 7) If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, go to next step.
2. Inspect ECU-B1 fuse in engine compartment relay/fuse block. If fuse is okay, go to next step. If fuse is blown, correct cause and replace fuse.
3. Inspect ECU-B2 fuse in passenger side interior fuse block. If fuse is blown, correct cause and replace fuse. If fuse is okay, repair White/Red wire between ECU-2B fuse and A/C control assembly connector terminal A13-1.

BLOWER MOTOR CIRCUIT

1. Turn ignition off. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-125255-S24344812912001100400000) under REMOVAL & INSTALLATION. Turn ignition on. Operate blower motor.
2. Backprobe between A/C control assembly connector terminal A13-4 (Red/Blue wire) and ground. If voltage is 1-3 volts, no problem is indicated at this time. If voltage is not as specified, go to next step.
3. Remove blower motor. See «BLOWER MOTOR R & I»(ref-125255-S06691750162001100400000) under REMOVAL & INSTALLATION. Connect battery voltage to terminal No. 2 (Red wire) of blower motor. Connect terminal No. 1 (Black wire) to ground. If blower motor runs smoothly, go to next step. Replace blower motor if it does not run smoothly.
4. Remove blower motor relay, leaving harness connector attached. Relay is located on blower motor case. Turn ignition on. Backprobe between relay terminals as specified. See «BLOWER MOTOR CONTROL RELAY SPECIFICATIONS»(ref-125255-S13981967612001100400000) table. (Scheme 19) Replace relay as necessary.
5. If relay is okay, inspect wiring between heater main relay and A/C control assembly. Repair wiring as necessary.

BLOWER MOTOR CONTROL RELAY SPECIFICATIONS

Scheme 19

COMPRESSOR CIRCUIT

1. Access Engine Control Module (ECM) located at left front corner of engine compartment. Leave harness connectors attached. Start engine. Backprobe ECM connector terminal E5-13 (Blue/Orange wire) and ground. (Scheme 20) Measure voltage while turning A/C switch on and off. See «A/C CLUTCH CIRCUIT VOLTAGE SPECIFICATIONS»(ref-125255-S25065861022001100400000) table. A/C CLUTCH CIRCUIT VOLTAGE SPECIFICATIONS Switch Position Volts ON 10-14 OFF 0
2. If voltage is as specified, temporarily substitute a known-good ECM and or A/C control unit, then retest system. If voltage is not as specified, disconnect magnetic clutch harness connector and go to next step.
3. Connect battery voltage to compressor clutch connector terminal No. 3 (Blue/White wire). (Scheme 21) If clutch engages, go to next step. Repair or replace clutch if it does not engage.
4. Inspect wiring harness and connectors between A/C compressor clutch harness connector and A/C compressor clutch relay (Blue/White wire). Repair as necessary. If wiring harness and connectors are okay, go to next step.
5. Inspect wiring harness and connectors between A/C compressor clutch relay and ECM (Blue/Orange wire). Repair as necessary. If wiring harness and connectors are okay, go to next step.
6. Inspect wiring harness and connectors between ECM and A/C control assembly terminal A13-5 (Blue wire). Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good ECM and/or A/C control assembly. Retest system.

Scheme 20

Scheme 21

COMPRESSOR CLUTCH RELAY

1. Remove compressor clutch relay. Relay is located on left side of engine compartment. Inspect for continuity between terminals No. 3 and 5. (Scheme 22) Continuity should not exist. Inspect for continuity between terminals No. 1 and 2. Continuity should exist.
2. Connect battery voltage to terminal No. 1. Connect terminal No. 2 to ground. Inspect for continuity between terminals No. 3 and 5. Continuity should exist. Replace relay if it does not operate as specified.

Scheme 22

COMPRESSOR LOCK SENSOR

Raise and support vehicle. Unplug compressor lock sensor connector, located at compressor. Measure resistance between sensor terminals No. 1 (Gray wire) and No. 2 (White/Black wire) at specified temperatures. See COMPRESSOR LOCK SENSOR SPECIFICATIONS table. Replace sensor if resistance is not as specified.

COMPRESSOR LOCK SENSOR SPECIFICATIONS

EXHAUST GAS SENSOR

Remove exhaust gas sensor. Connect battery positive to exhaust sensor terminal No. 4 and battery negative to terminal No. 1. (Scheme 23) Apply voltage for more than 30 seconds, then measure resistance between terminals No. 2 and No. 3. Resistance should be 5-100 k/ohms at 50-95°F (10-35°C). If resistance is not as specified, replace sensor.

Scheme 23

HEATER MAIN RELAY

1. Remove heater main relay. Relay is located on left side of engine compartment. Inspect for continuity between terminals No. 5 and 4. (Scheme 24) Continuity should not exist. Inspect for continuity between terminals No. 2 and 4 and terminals No. 1 and 3. Continuity should exist.
2. Connect battery voltage to terminal No. 1. Connect terminal No. 3 to ground. Inspect for continuity between terminals No. 5 and 4. Continuity should exist. Replace relay if it does not operate as specified.

Scheme 24

IN-VEHICLE TEMPERATURE SENSOR

Remove panel underneath left side of instrument panel. Unplug in-vehicle temperature sensor. Measure sensor resistance while heating sensor. See IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace in-vehicle temperature sensor.

IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS

OUTSIDE TEMPERATURE SENSOR

1. Remove clip and outside temperature sensor from lower bumper reinforcement. Unplug outside temperature sensor connector. Measure the sensor resistance while heating the sensor. See «OUTSIDE TEMPERATURE SENSOR SPECIFICATIONS»(ref-125255-S17102880822001100400000) table.
2. If resistance is not as specified, replace sensor. If resistance is within specification, inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, substitute a known-good A/C control assembly, then retest system. If problem does not exist with known-good A/C control assembly, replace original A/C control assembly.

OUTSIDE TEMPERATURE SENSOR SPECIFICATIONS

RADIATOR FAN NO. 2 RELAY

1. Remove radiator fan No. 2 relay. Relay is located on left side of engine compartment. Inspect for continuity between terminals No. 3 and 5. (Scheme 25) Continuity should not exist. Inspect for continuity between terminals No. 1 and 2 and terminals No. 3 and 4. Continuity should exist.
2. Connect battery voltage to terminal No. 1. Connect terminal No. 2 to ground. Inspect for continuity between terminals No. 3 and 5. Continuity should exist. Replace relay if it does not operate as specified.

Scheme 25

RADIATOR FAN NO. 3 RELAY

1. Remove radiator fan No. 3 relay. Relay is located on left side of engine compartment. Inspect for continuity between terminals No. 3 and 5. (Scheme 24) Continuity should not exist. Inspect for continuity between terminals No. 1 and 2. Continuity should exist.
2. Connect battery voltage to terminal No. 1. Connect terminal No. 2 to ground. Inspect for continuity between terminals No. 3 and 5. Continuity should exist. Replace relay if it does not operate as specified.

RADIATOR FAN MAIN RELAY

1. Remove radiator fan main relay. Relay is located in relay box, on right side of engine compartment, in front of battery. Inspect for continuity between terminals No. 5 and 4. (Scheme 24) Continuity should not exist. Inspect for continuity between terminals No. 2 and 4, and terminals No. 1 and 3. Continuity should exist.
2. Connect battery voltage to terminal No. 1. Connect terminal No. 3 to ground. Inspect for continuity between terminals No. 5 and 4. Continuity should exist. Replace relay if it does not operate as specified.

SOLAR SENSOR

1. Remove solar sensor and unplug sensor harness connector. Cover sensor with cloth. Connect positive lead of ohmmeter to sensor terminal No. 1, and negative lead to terminal No. 2. (Scheme 26) Measure and record resistance between sensor terminals.
2. Remove cloth. Subject sensor to bright light. Again measure sensor. See «SOLAR SENSOR RESISTANCE SPECIFICATIONS»(ref-125255-S02081497512001100400000) table. If resistance is not as specified, replace sensor.

SOLAR SENSOR RESISTANCE SPECIFICATIONS

Scheme 26

ENGINE COOLANT TEMPERATURE SWITCH

Remove engine coolant temperature switch located in lower radiator header. Using an ohmmeter, measure resistance between sensor terminals at specified temperatures. See ENGINE COOLANT TEMPERATURE SWITCH RESISTANCE SPECIFICATIONS table.

ENGINE COOLANT TEMPERATURE SWITCH RESISTANCE SPECIFICATIONS