AIR CONDITIONING SYSTEM (for Cold Area) TERMINALS OF ECU


  1. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY (w/ HOT GAS HEATER)

    A01DXXBE03

    1. Disconnect the A9 air conditioning amplifier connector.

    2. Measure the voltage and resistance of the wire harness side connector.

      Symbols (Terminal No.) Wiring Color Terminal Description Condition Specified Condition
      +B (A9-40) - GND (A9-29) L-Y - L For memory backup Always 10 to 14 V
      IG+ (A9-20) - GND (A9-29) R-L - L Power source (IG) Ignition switch OFF Below 1 V
      IG+ (A9-20) - GND (A9-29) R-L - L Power source (IG) Ignition switch ON 10 to 14 V
      GND (A9-29) - Body ground L - Body ground Ground Always Below 1 Ω
      ACON (A9-8) - GND (A9-29) R-G - L A/C switch signal A/C switch OFF Below 1 V
      ACON (A9-8) - GND (A9-29) R-G - L A/C switch signal

      Ignition switch START

      Blower switch ON

      A/C switch ON

      		 10 to 14 V
      IND- (A9-9) - GND (A9-29) R-L - L A/C indicator light signal A/C switch OFF Below 1 V
      IND- (A9-9) - GND (A9-29) R-L - L A/C indicator light signal

      Ignition switch START

      Blower switch ON

      A/C switch ON

      		 10 to 14 V
      BLW (A9-38) - GND (A9-29) R-L - L Max HOT switch signal Temperature control knob: Max HOT Below 1 Ω
      BLW (A9-38) - GND (A9-29) R-L - L Max HOT switch signal Temperature control knob: Max HOT 10k Ω or higher
      HEAT (A9-5) - GND (A9-29) L-O - L Heater switch signal Heater switch ON Below 1 Ω
      HEAT (A9-5) - GND (A9-29) L-O - L Heater switch signal Heater switch OFF 10k Ω or higher
      MGC (A9-19) - GND (A9-29) B - L Magnet clutch relay signal

      Ignition switch START

      Blower switch ON

      		 10 to 14 V
      MGC (A9-19) - GND (A9-29) B - L Magnet clutch relay signal

      Ignition switch START

      Blower switch OFF

      		 Below 1 V
      TAIL (A9-7) - GND (A9-29) G - L Light control switch signal Light control switch ON 10 to 14 V
      TAIL (A9-7) - GND (A9-29) G - L Light control switch signal Light control switch OFF Below 1 V

      • If the result is not as specified, there may be a malfunction on the wire harness side.

    3. Reconnect the A9 connector.

    4. Measure the voltage and resistance of the connector.

      Symbols (Terminal NO.) Wiring Color Terminal Description Condition Specified Condition
      S5 (A9-13) - SG-3 (A9-12) R-B - BR-Y Power supply for pressure sensor Ignition switch ON 4.5 to 5.5 V
      PRE (A9-4) - SG-3 (A9-12) BR - BR-Y Air conditioner pressure switch signal

      Ignition switch START

      Refrigerant pressure normal: 0.18 MPa (1.9 kgf/cm2, 26 psi) to 3.03 MPa (31.0 kgf/cm2, 440 psi)

      Blower switch ON

      A/C switch ON

      		 0.74 to 4.66 V
      PRE (A9-4) - SG-3 (A9-12) BR - BR-Y Air conditioner pressure switch signal

      Ignition switch START

      Blower switch ON

      A/C switch ON

      Refrigerant pressure abnormal: pressure less than 0.18 MPa (1.9 kgf/cm2, 26 psi)

      		 Below 0.74 V
      PRE (A9-4) - SG-3 (A9-12) BR - BR-Y Air conditioner pressure switch signal

      Ignition switch START

      Blower switch ON

      A/C switch ON

      Refrigerant pressure abnormal: pressure more than 3.03 MPa (31.0 kgf/cm2, 440 psi)

      		 Above 4.66 V
      TAM (A9-25) - SG-3 (A9-12) W-G - BR-Y Ambient temperature sensor signal

      Ignition switch ON

      Ambient temperature is 25 °C (77°F)

      		 1.35 to 1.75 V
      SG-3 (A9-12) - Body ground BR-Y - Body ground Ground for Ambient temperature sensor and pressure sensor Always Below 1 Ω
      MGC (A9-19) - GND (A9-29) B - L Magnet clutch signal

      Ignition switch START

      Magnet clutch is engaged

      		 10 to 14 V
      MGC (A9-19) - GND (A9-29) B - L Magnet clutch signal

      Ignition switch START

      Magnet clutch is not engaged

      		 Below 1 V
      TE (A9-24) - SG-1 (A9-31) G - P Evaporator temperature sensor signal

      Ignition switch ON

      Evaporator temperature is 0°C (32°F)

      		 2.0 to 2.4 V
      TE (A9-24) - SG-1 (A9-31) G - P Evaporator temperature sensor signal

      Ignition switch ON

      Evaporator temperature is 15 °C (59°F)

      		 1.4 to 1.8 V
      SG-1 (A9-31) - Body ground P - Body ground Ground for evaporator temperature sensor Always Below 1 Ω
      ACT (A9-39) - GND (A9-29) R-L - L Magnet on permit signal

      Ignition switch START

      Blower switch OFF

      A/C switch OFF

      		 Below 1 V
      ACT (A9-39) - GND (A9-29) R-L - L Magnet on permit signal

      Ignition switch START

      Blower switch ON

      A/C switch ON

      		 10 to 14 V
      AC1 (A9-39) - GND (A9-29) Y - L Idle-up request signal

      Ignition switch START

      Magnet clutch is not engaged

      		 Below 1 V
      AC1 (A9-39) - GND (A9-29) Y - L Idle-up request signal

      Ignition switch START

      Magnet clutch is engaged

      		 10 to 14 V
      BLW (A9-38) - GND (A9-29) R-1 - L Max HOT switch signal

      Ignition switch ON

      Temperature control knob: Max HOT

      		 10 to 14 V
      BLW (A9-38) - GND (A9-29) R-1 - L Max HOT switch signal

      Ignition switch ON

      Temperature control knob: except Max HOT

      		 Below 1 V
      HEAT (A9-5) - GND (A9-29) L-O - L Heater switch input signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or lower

      		 Below 1 V
      HEAT (A9-5) - GND (A9-29) L-O - L Heater switch input signal

      Ignition switch START

      Temperature control knob: except Max HOT

      Heater switch OFF

      Blower switch ON

      Coolant temperature 65 °C (149°F) or lower

      		 10 to 14 V
      SWIN (A9-15) - GND (A9-29) P - L Heater switch indicator light signal

      Ignition switch START

      Temperature control knob: Max HOT

      Heater switch ON

      Blower switch ON

      Coolant temperature 65 °C (149°F) or lower

      		 Below 1 V
      SWIN (A9-15) - GND (A9-29) P - L Heater switch indicator light signal

      Ignition switch START

      Temperature control knob: except Max HOT

      Heater switch OFF

      Blower switch ON

      Coolant temperature 65 °C (149°F) or lower

      		 10 to 14 V
      MGV (A9-17) - GND (A9-29) Y-B - L Magnetic valve operating signal Ignition switch ON 10 to 14 V
      MGV (A9-17) - GND (A9-29) G - L Magnetic valve operating signal

      Ignition switch START

      Temperature Control knob: Max HOT

      A/C switch ON

      Blower switch ON

      Heater switch ON

      Coolant temperature 65 °C (149°F) or lower

      		 Below 1 V
      ALT (A9-37) - GND (A9-29) G - L Generator Engine running Pulse generation
      PTCR (A9-26) - GND (A9-29) L-W - L Heater switch output signal

      Ignition switch START

      Temperature Control knob: Max HOT

      Heater switch ON

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 10 to 14 V
      PTCR (A9-26) - GND (A9-29) L-W - L Heater switch output signal

      Ignition switch START

      Temperature Control knob: Max HOT

      Heater switch OFF

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 Below 1 V
      TW (A9-32) - GND (A9-29) P - L Water temperature signal Ignition switch ON Pulse generation
      TACO (A9-33) - GND (A9-29) B-W - L Tachometer signal Engine running

      Pulse generation

      (see waveform 1)
      PTC1 (A9-3) - GND (A9-29) R-W - L PTC heater relay signal

      Ignition switch START

      Heater switch ON

      Temperature Control knob: Max HOT

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 Below 1 V
      PTC1 (A9-3) - GND (A9-29) GR - L PTC heater relay signal

      Ignition switch START

      Heater switch OFF

      Temperature Control knob: Max HOT

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 10 to 14 V
      PTC2 (A9-2) - GND (A9-29) GR - L PTC heater relay signal

      Ignition switch START

      Heater switch ON

      Temperature Control knob: Max HOT

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 Below 1 V
      PTC2 (A9-2) - GND (A9-29) GR - L PTC heater relay signal

      Ignition switch START

      Heater switch OFF

      Temperature Control knob: Max HOT

      Coolant temperature 65 °C (149°F) or lower

      Blower switch ON

      		 10 to 14 V

      • If the result is not as specified, the air conditioning amplifier may have a malfunction.

    5. A01E1EAE03

      Inspect using an oscilloscope.


      1. Waveform 1 (Reference)

        Item Content
        Symbols (Terminal No.) TACO (A9-33) - GND (A9-29)
        Tool Setting 5 V/DIV., 20 msec./DIV.
        Condition Engine idling

        Tech Tips

        As engine speed increases, the wavelength shortens.

  2. CHECK HEATER AMPLIFIER ASSEMBLY (w/ Viscous Heater)

    A01DXD5E01

    1. Disconnect the V6 viscous heater amplifier connector.

    2. Measure the voltage and resistance of the wire harness side connector.

      Symbols (Terminal NO.) Wiring Color Terminal Description Condition Specified Condition
      +B (V6-9) - GND (V6-15) L-Y - L Viscous heater MGC power supply Always 10 to 14 V
      IG (V6-1) - GND (V6-15) R-L- L Power source (IG) Ignition switch OFF Below 1 V
      IG (V6-1) - GND (V6-15) R-L- L Power source (IG) Ignition switch ON 10 to 14 V
      GND (V6-15) - Body ground L - Body ground Ground Always Below 1 Ω
      BLW (V6-2) - GND (V6-15) R-L - L Max HOT switch signal Temperature control knob: Max HOT Below 1 Ω
      BLW (V6-2) - GND (V6-15) R-L - L Max HOT switch signal Temperature control knob: except Max HOT 10k Ω or higher
      HLS (V6-10) - GND (V6-15) G - L Light control switch signal Light control switch ON 10 to 14 V
      HLS (V6-10) - GND (V6-15) G - L Light control switch signal Light control switch OFF Below 1 Ω

      • If the result is not as specified, there may be a malfunction on the wire harness side.

    3. Reconnect the V6 viscous heater amplifier connector.

    4. Measure the voltage and resistance of the wire harness side connector

      Symbols (Terminal NO.) Wiring Color Terminal Description Condition Specified Condition
      MGCA (V6-18) - GND (V6-15) B -L Magnet clutch signal

      Ignition switch START

      Magnet clutch is engaged

      		 Below 1 V
      MGCA (V6-18) - GND (V6-15) B -L Magnet clutch signal

      Ignition switch START

      Magnet clutch is not engaged

      		 10 to 14 V
      ACT (V6-12) - GND (V6-15)

      R-L - L*1

      V - L*2

      		 Viscous heater permit signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 Below 1 V
      ACT (V6-12) - GND (V6-15)

      R-L - L*1

      V - L*2

      		 Viscous heater permit signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch OFF

      Coolant temperature 65 °C (149°F) or more

      		 10 to 14 V
      AC2 (V6-5) - GND (V6-15) BR - L Viscous heater ON signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 Above 7.8 V
      AC2 (V6-5) - GND (V6-15) BR - L Viscous heater ON signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 Below 1 V
      BLW (V6-2) - GND (V6-15) R-L - L Max HOT switch signal

      Ignition switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      		 10 to 14 V
      BLW (V6-2) - GND (V6-15) R-L - L Max HOT switch signal

      Ignition switch ON

      Temperature control knob: except Max HOT

      Blower switch ON

      		 Below 1 V
      SWVC (V6-13) - GND (V6-15) L-O - L Heater switch input signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 Below 1 V
      SWVC (V6-13) - GND (V6-15) L-O - L Heater switch input signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 10 to 14 V
      SWIN (V6-8) - ND (V6-15) P - L Heater switch indicator light signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 10 to 14 V
      SWIN (V6-8) - GND P - L Heater switch indicator light signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch ON

      Coolant temperature 65 °C (149°F) or more

      		 Below 1 V
      TW (V6-4) - GND (V6-15) P - L Water temperature signal Ignition switch START Pulse generation
      TACO (V6-11) - GND (V6-15) B-W - L Tachometer signal Engine running

      Pulse generation

      (see waveform 1)
      ALT (V6-14) - GND (V6-15) G - L Generator Engine running Pulse generation
      PCT1 (V6-6) - GND (V6-15) R-W - L PTC heater relay signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature: 65°C (149°F) or lower

      		 10 to 14 V
      PTC1 (V6-6) - GND (V6-15) R-W - L PTC heater relay signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch OFF

      Coolant temperature: 65°C (149°F) or lower

      		 Below 1 V
      PTC2 (V6-7) GND (V6-15) GR - L PTC heater relay signal

      Ignition switch START

      Heater switch ON

      Temperature control knob: Max HOT

      Blower switch ON

      Coolant temperature: 65°C (149°F) or lower

      		 10 to 14 V
      PTC2 (V6-7) - GND (V6-15) GR - L PTC heater relay signal

      Ignition switch START

      Heater switch OFF

      Temperature control knob: except Max HOT

      Blower switch OFF

      Coolant temperature: 65°C (149°F) or lower

      		 Below 1 V

      • *1: LHD

      • *2: RHD

      If the result is not as specified, the heater amplifier may have a malfunction.

    5. Inspect using an oscilloscope.


      1. A01E1EAE03

        Waveform 1 (Reference)

        Item Content
        Symbols (Terminal No.) TACO (V6-11) - GND (V6-15)
        Tool Setting 5 V/DIV., 20 msec./DIV.
        Condition Engine idling

        Tech Tips

        As engine speed increases, the wavelength shortens.

  3. CHECK ECM

    A01DYXUE24

    1. Measure the voltage of the connectors.


      1. 2KD-FTV

        w/ Hot gas heater
        Symbols (Terminal NO.) Wiring color Terminal Description Condition Specified Condition
        ACT (E6-19) - E01 (E8-7) R-L - W-B Magnet on permit signal

        Ignition switch START

        Heater switch OFF

        Blower switch ON

        A/C switch OFF

        		 Below 1 V
        ACT (E6-19) - E01 (E8-7) R-L - W-B Magnet on permit signal

        Ignition switch START

        Heater switch ON

        Blower switch ON

        A/C switch ON

        		 10 to 14 V
        AC1 (E6-18) - E01 (E8-7) Y - W-B Idle-up request signal

        Ignition switch START

        Magnet clutch is engaged

        		 Below 1 V
        AC1 (E6-18) - E01 (E8-7) Y - W-B Idle-up request signal

        Ignition switch START

        Magnet clutch is not engaged

        		 10 to 14 V
        HSW (E6-20) - E01 (E8-7) L-W - W-B Heater switch output signal for idle-up

        Ignition switch START

        Blower switch ON

        Power heater switch ON

        Temperature control knob: Max HOT

        		 Below 1 V
        HSW (E6-20) - E01 (E8-7) L-W - W-B Heater switch output signal for idle-up

        Ignition switch START

        Blower switch OFF

        Power heater switch OFF

        Temperature control knob: Max HOT

        		 10 to 14 V
        THWO (E5-2) - E01 (E8-7) P -W-B Ignition switch ON Ignition switch START Pulse generation
        TACH (E5-4) - E01 (E8-7) B-W - W-B Tachometer signal Engine running Pulse generation (see waveform 1)
        w/ Viscous heater
        Symbols (Terminal NO.) Wiring color Terminal Description Condition Specified Condition
        ACT (E6-19) - E01 (E8-7)

        R-L - W-B*1

        V - W-B*2

        		 Viscous heater permit signal

        Ignition switch START

        Heater switch OFF

        Blower switch ON

        Coolant temperature: 65°C (149°F) or lower

        Temperature control knob: except Max HOT

        		 Below 1 V
        ACT (E6-19) - E01 (E8-7)

        R-L - W-B*1

        V - W-B*2

        		 Viscous heater permit signal

        Ignition switch START

        Heater switch ON

        Blower switch ON

        Coolant temperature: 65°C (149°F) or lower

        Temperature control knob: Max HOT

        		 10 to 14 V
        AC1 (E6-18) - E01 (E8-7) BR - W-B Viscous heater on signal

        Ignition switch START

        Viscous magnet clutch is engaged

        		 Below 1 V
        AC1 (E6-18) - E01 (E8-7) BR - W-B Viscous heater on signal

        Ignition switch START

        Viscous magnet clutch is not engaged

        		 10 to 14 V
        THWO (E5-2) - E01 (E8-7) P -W-B Ignition switch ON Ignition switch START Pulse generation
        TACH (E5-4) - E01 (E8-7) B-W - W-B Tachometer signal Engine running Pulse generation (see waveform 1)

        Tech Tips

        *1: LHD

        *2: RHD


        • If the result is not as specified, the ECM may have a malfunction.

    2. A01E1EAE03

      Inspect using an oscilloscope.


      1. Waveform 1 (Reference)

        Item Content
        Symbols (Terminal No.) TACH (E5-4) - E01 (E8-7)
        Tool Setting 5 V/DIV., 20 msec./DIV.
        Condition Engine idling

        Tech Tips

        As engine speed increases, the wavelength shortens.