Page 723 of 1500

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-22
DTC B1021, B1022: Air Thermo Sensor System
.
DTC SET CONDITION
DTC B1021 is set if there is a short circuit in the
air thermo sensor input circuit.
DTC B1022 is set if there is a defective connector
connection, or if there is an open circuit in the
harness.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
The A/C-ECU, the air thermo sensor, or connec-
tor(s) or wiring between the two may be defec-
tive.Past trouble
If DTC B1021 or B1022 is stored as a past trou-
ble, carry out diagnosis with particular emphasis
on wiring and connector(s) between the A/C-ECU
and the air thermo sensor. If the connectors and
wiring are normal, and obviously the ECU is the
cause of the trouble, replace the ECU. If in doubt,
do not replace the ECU.
TROUBLESHOOTING HINT
Malfunction of connector.
Malfunction of the harness.
Malfunction of the air thermo sensor.
Malfunction of the A/C-ECU.
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
Page 727 of 1500
AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-26
STEP 5. Check the wiring harness between A/C-ECU
connector C-15 (terminal 20), C-16 (terminal 24) and air
thermo sensor connector C-126 (terminals 2 and 1).
Q: Is the wiring harness between A/C-ECU connector C-10
(terminal 10 and 13) and air thermo sensor connector
C-126 (terminals 2 and 1) in good condition?
YES : Go to Step 6.
NO : Repair the wiring harness. Then go to Step 7.
Page 729 of 1500

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-28
DTC B1041, B1042: Air Mixing Damper Control Motor and Potentiometer (Potentiometer system)
.
DTC SET CONDITION
DTC B1041 or B1042 is set if there is an open or
short circuit in the potentiometer input circuit, or if
there is an open circuit in the power circuit or
earth circuit.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
The A/C-ECU, the air mixing damper control
motor and potentiometer, or connector(s) or wir-
ing between the two may be defective.Past trouble
If DTC B1041 or B1042 is stored as a past trou-
ble, carry out diagnosis with particular emphasis
on wiring and connector(s) between the A/C-ECU
and the air mixing damper control motor and
potentiometer. If the connectors and wiring are
normal, and obviously the ECU is the cause of
the trouble, replace the ECU. If in doubt, do not
replace the ECU.
TROUBLESHOOTING HINT
Malfunction of connector.
Malfunction of the harness.
Malfunction of the air mixing damper control
motor and potentiometer.
Malfunction of the A/C-ECU.
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
DIAGNOSIS
Required Special Tool:
: Diagnostic Tool (MUT-III Sub Assembly)
MB991824: Vehicle Communication Interface (V.C.I.)
MB991827: MUT-III USB Cable
MB991910: MUT-III Main Harness A (Vehicles with CAN
communication system)
Page 733 of 1500
AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-32
STEP 5. Check the wiring harness between A/C-ECU
connectors C-15 (terminals 16 and 20), C-16 (terminal 29)
and air mixing damper control motor and potentiometer
connector C-105 (terminals 5, 7 and 3).
Q: Are the wiring harness between A/C-ECU connector
C-15 (terminals 16 and 20), C-16 (terminal 29) and air
mixing damper control motor and potentiometer
connector C-105 (terminals 5, 7 and 3) in good
condition?
YES : Go to Step 6.
NO : Repair the wiring harness. Then go to Step 7.
Page 736 of 1500

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-35
DTC B1045: Air mixing damper control motor and potentiometer (activating system failure)
.
DTC SET CONDITION
If the air mixing damper control motor does not
work normally, DTC No.B1045 will be set.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
The A/C-ECU, the air mixing damper control
motor and potentiometer, or connector(s) or wir-
ing between the two may be defective.Past trouble
If DTC B1045 is stored as a past trouble, carry
out diagnosis with particular emphasis on wiring
and connector(s) between the A/C-ECU and the
air mixing damper control motor and potentiome-
ter. If the connectors and wiring are normal, and
obviously the ECU is the cause of the trouble,
replace the ECU. If in doubt, do not replace the
ECU.
TROUBLESHOOTING HINT
Malfunction of connector.
Malfunction of the harness.
Malfunction of the air mixing damper control
motor and potentiometer.
Malfunction of the A/C-ECU.
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
Page 739 of 1500
AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-38
STEP 5. Check the wiring harness between A/C-ECU
connectors C-15 (terminal 1 and 2) and air mixing damper
control motor and potentiometer connector C-105
(terminals 1 and 2).
Q: Are the wiring harness between A/C-ECU connectors
C-15 (terminals 1 and 2) and air mixing damper control
motor and potentiometer connector C-105 (terminals 1
and 2) in good condition?
YES : Go to Step 6.
NO : Repair the wiring harness. Then go to Step 7.
Page 742 of 1500

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-41
DTC B1061, B1062: Mode Selection Damper Control Motor and Potentiometer
.
DTC SET CONDITION
DTC B1061 or B1062 is set if there is an open or
short circuit in the potentiometer input circuit, or if
there is an open in the power circuit or ground cir-
cuit.
.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
The A/C-ECU, the mode selection damper con-
trol motor and potentiometer, or connector(s) or
wiring between the two may be defective.Past trouble
If DTC B1061 or B1062 is stored as a past trou-
ble, carry out diagnosis with particular emphasis
on wiring and connector(s) between the A/C-ECU
and the mode selection damper control motor
and potentiometer. If the connectors and wiring
are normal, and obviously the ECU is the cause
of the trouble, replace the ECU. If in doubt, do not
replace the ECU.
TROUBLESHOOTING HINT
Malfunction of connector.
Malfunction of the harness.
Malfunction of the mode selection damper control
motor and potentiometer.
Malfunction of the A/C-ECU.
Refer to component locations GROUP-70
Refer to configuration diagrams GROUP-80
Refer to circuit diagrams GROUP-90
Page 746 of 1500
AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-45
STEP 5. Check the wiring harness between A/C-ECU
connectors C-15 (terminals 16 and 20), C-21 (terminal 21)
and mode selection damper control motor and
potentiometer connector C-102 (terminals 5, 7 and 3).
Q: Are the wiring harnesses between A/C-ECU connectors
C-10 (terminals 15, 11 and 10) and mode selection
damper control motor and potentiometer connector
C-102 (terminals 5, 7 and 3) in good condition?
YES : Go to Step 6.
NO : Repair the wiring harness. Then go to Step 7.