2008 SUZUKI SWIFT communication

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Auto A/C Electronic Control Input / Output Table
HVAC Control Module Operation DescriptionS7RS0B7221002
Temperature Control
HVAC control module calculates the target temperature
control door position based on signals from the
temperature selector, inside air temperature sensor,
outside air temperature sensor and sunload sensor and
controls the temperature control actuator so that the
current position of the temperature control door matches
its target position.
Fan Speed Control
HVAC control module calculates the target blower fan
speed based on signals from the temperature selector,
inside air temperature sensor, outside air temperature
sensor and sunload sensor, compares it with the current
blower fan speed inputted from the blower motor
controller to control the current blower fan speed to the
target level.
Air Flow Outlet Control
HVAC control module calculates the target temperature
control door position based on signals from the
temperature selector, inside air temperature sensor,
outside air temperature sensor and sunload sensor.
Using thus obtained target temperature control door
position, it further calculates the target air flow control
door position and controls the ai r flow control actuator so
that the current air flow c ontrol door position becomes
the target position. Air Intake Position Control
HVAC control module determines the position of the air
intake control door based on signals from the
temperature selector, inside air temperature sensor,
outside air temperature sensor and sunload sensor and
selects any of the following positions by controlling the
position of the air intake control door.
• FRESH position (FRE)
• RECIRCULATION position (REC)
• MIX position (MIX)
Refrigerant Type IdentificationS7RS0B7221003
Refer to “Refrigerant Type Identification”.
Sub-Cool A/C System DescriptionS7RS0B7221005
Refer to “Sub-Cool A/C System Description”.
A/C Operation DescriptionS7RS0B7221006
Refer to “A/C Operation Description”.
Sunload sensor
Outside air temperature sensor Evaporator temperature sensor
A/C refrigerant pressure sensor
Temperature selector
MODE (air flow) selector
Blower speed selector
Air intake selector
AUTO switch
A/C switch
Compressor
Blower motor controller
Temperature control actuator
Air flow control actuator
Air intake control actuator
BCM
ECM
Data link connector
HVAC control module
CPU
ECT sensor
Inside air temperature sensor
VSS
*
I5RS0C722002-02
*: CAN communication

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On-Board Diagnostic System DescriptionS7RS0B7221007
NOTE
The diagnostic information as diagnostic
trouble code (DTC) can be known by using
SUZUKI scan tool. For further details, refer to
“DTC Check”.

HVAC control module detect s malfunctions, which may
occur in the following area.
• Outside air temperature sensor
• Inside air temperature sensor
• Evaporator temperature sensor
• Sunload sensor
• ECT sensor
• Temperature control actuator of HVAC unit
• Air flow control actuator of HVAC unit
• A/C refrigerant pressure sensor • HVAC control module
• VSS
• Serial Communication line
• CAN communication line
When HVAC control module detects malfunction, the
“AUTO” indicator lamp (1) flashes to warn and the
diagnostic trouble code (DTC) is stored in the memory of
the module. When diagnosing trouble, the DTC can be
checked according to “DTC Check”.
Schematic and Routing Diagram
Major Components of A/C SystemS7RS0B7222001
Refer to “Major Components of A/C System”.
1
I5RS0A722003-01

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3) Light over sunload sensor vertically with an incandescent lamp approximately 100 W apart from
about 100 mm (3.94 in.).
NOTE
If sunload sensor is not lighted over with an
incandescent lamp, DTC B1504 is detected
as current DTC even though there is not any
malfunction.

4) Turn ignition switch to ON position.
5) Erase DTC according to instructions displayed on SUZUKI scan tool.
NOTE
To know how to use SUZUKI scan tool, refer
to operator’s manual for SUZUKI scan tool.

6) After completing the clearance, turn ignition switch to OFF position, and then di sconnect SUZUKI scan
tool from DLC.
Not Using SUZUKI Scan Tool 1) Turn ignition switch to ON position.
2) Set temperature selector to 25 °C (77 °F). 3) Push AUTO switch (1) and
MODE (air flow) selector
(2) at the same time to have history DTC displayed.
4) Push MODE (air flow) selector (2) and OFF switch (3) at the same time while history DTC is displayed.
5) Check that “CL” (4) appears on display. “CL” means that DTC has been cleared.
DTC TableS7RS0B7224005
CAUTION!
Be sure to perform “Air Conditioning Sy stem Check” before starting diagnosis.

1
2
3
2
4
I5RS0A722008-01
DTC No.
(displayed on
SUZUKI
scan tool) DTC
(indicated on
display of HVAC
control
module) Priority of
display
(current DTC) Priority
of
display
(history DTC) Diagnosis
“AUTO”
indicator lamp
) B1502 21 1 1 Inside air temperature sensor and/or its
circuit malfunction Open
Flashed
22 2 2 Short
) B1503 31 3 3 Evaporator temperature sensor and/or its
circuit malfunction Open
Flashed
32 4 4 Short
) B1504 41 21 — Sunload sensor and/or its circuit
malfunction Open —
42 5 5 Short Flashed
) B1511 61 6 6 Temperature control actuator (position
sensor) and/or its circuit malfunction Open
Flashed
62 7 7 Short
) B1512 71 8 8 Air flow control actuator (position sensor)
and/or its circuit malfunction Open
Flashed
72 9 9 Short
) B1513 63 10 10 Temperature control actuator and/or its circuit malfunction Flashed
) B1514 73 11 11 Air flow control actuator and/or its circuit malfunction Flashed
) B1541 E1 12 — HVAC control module back-up power supply malfunction —
) B1546 d5 22 — A/C refrigerant pressure malfunction —
) B1551 91 13 12
Serial communication circuit malfunction Open
Flashed
92 14 13 Short
) B1552 94 15 14 Serial communication signal malfunction Flashed
) B1553 A4 16 15 CAN communication signal malfunction Flashed
) B1557 b4 19 16 Vehicle speed sensor signal malfunction —
) B1561 54 17 17 Engine coolant temperature sensor signal malfunction Flashed

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NOTE
When no current DTC is detected, all contents displayed on display (1) of HVAC control module and
defroster indicator (2) flash at the same time.

Fail-Safe TableS7RS0B7224006
When any of the following malfunctions (DTCs) is detected, fail-safe mode is activated.
However, when HVAC control module detects normal ope ration of A/C system, fail-safe mode is cancelled.
)
B1562 14 18 18 Outside air temperatur e sensor signal malfunction Flashed
) B1563 d4 20 19 A/C refrigerant pressure sensor signal malfunction —
— See NOTE
below
(current DTC) ——Normal —
00 (history DTC)
DTC No.
(displayed on
SUZUKI
scan tool) DTC
(indicated on
display of HVAC
control
module) Priority of
display
(current DTC) Priority
of
display
(history DTC) Diagnosis
“AUTO”
indicator lamp
1
2
I5RS0A722009-01
DTC No.
Trouble Area Fail-Safe Operation
)
B1502 Inside air temperature sensor and/
or its circuit HVAC control module controls actu
ators assuming that inside air
temperature is 25 ° C (77 °F).
)
B1503 A/C evaporator temperature sensor
and its circuit • HVAC control module turn
s off A/C switch signal.
• HVAC control module controls actu ators assuming that evaporator
temperature is 0 ° C (32 °F).
)
B1504 Sunload sensor and/or its circuit HVAC control module controls actu
ators assuming that amount of
sunlight is 0 W/m
2.
) B1551 Serial communication circuit
HVAC control module controls actuators assuming that outside air
temperature is 20 ° C (68 °F), engine coolant temperature is 80 °C
(176 °F), and vehicle speed is 40 km/h (25 mph).
)
B1552 Serial communication circuit
)
B1553 CAN communication circuit
)
B1557 Vehicle speed sensor and/or its
circuit HVAC control module controls act
uators assuming that vehicle speed
is 40 km/h (25 mph).
)
B1561 Engine coolant temperature sensor
and/or its circuit HVAC control module controls act
uators assuming that engine coolant
temperature is 80 ° C (176 °F).
)
B1562 Outside air temperature sensor
and/or its circuit HVAC control module controls actu
ators assuming that outside air
temperature is 20 ° C (68 °F).

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DTC B1546: A/C Refrigerant Pressure MalfunctionS7RS0B7224018
DTC Detecting Condition and Trouble Area
DTC Troubleshooting
DTC B1551: Serial Communication Circuit MalfunctionS7RS0B7224019
Wiring DiagramDTC detecting condition Trouble area
A/C refrigerant pressure sensor signal voltage is lower t han specified value
even though outside air temperature is higher than specified value for
specified time continuously. • Insufficient of refrigerant
• A/C refrigerant pressure sensor
• Outside air temperature sensor
• HVAC control module
Step
Action YesNo
1 A/C refrigerant pressure and outside air temperature
check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Start engine and select “DATA LIST” mode on scan tool.
3) Check “Refrigerant Pressure” and “Outside Air Temp” varies displayed on scan tool.
Is displayed each va ries described varies in “Scan Tool
Data”? Go to Step 2.
Check the amount of
refrigerant and system
for leaks.
2 A/C system performance check
1) Check A/C system performance referring to “A/C System
Performance Inspection”.
Is check result satisfactory? Go to Step 3.
Repair or replace
defective part.
3 A/C refrigerant pressure sensor check
1) Check A/C refrigerant pressure sensor referring to “A/C
Refrigerant Pressure Sensor and Its Circuit Inspection”.
Is check result satisfactory? Go to Step 4.
A/C refrigerant pressure
sensor faulty.
4 Outside air temperature sensor check
1) Check outside air temperature sensor referring to
“Information Display (Clock) Removal and Installation in
Section 9C”.
Is check result satisfactory? HVAC control module
faulty.
Outside air temperature
sensor faulty.
YEL17812910
65 431516 14 13 12 11
G52
789101920121112
65 431718 16 15 14 13
G51
G51-7
12V
2
3
G37-11
I5RS0A722016-01
1. HVAC control module 2. BCM3. Information display

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DTC Detecting Condition and Trouble Area
DTC Troubleshooting
DTC B1552: Serial Communication Signal MalfunctionS7RS0B7224020
DTC Detecting Condition and Trouble AreaDTC detecting condition Trouble area
Serial communication signal is higher than or lower than specified value for
specified time continuously. • Serial communication line of BCM
• BCM (included in junction block
assembly)
• Information display
• HVAC control module
Step Action YesNo
1 DTC check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Disconnect connector from information display.
3) Turn ignition switch ON and check DTC.
Is there DTC B1551? Go to Step 2.
Information display
faulty.
2 Wire harness check
1) Disconnect connectors from BCM and HVAC control
module.
2) Measure resistance between “G37-11” terminal of BCM connector and “G51-7” terminal of HVAC control module
connector.
Is resistance below 5
Ω? Go to Step 3. “YEL” wire open or high
resistance circuit.
3 Wire harness check
1) Measure resistance between “G51-7” terminal of HVAC
control module connector and vehicle body ground.
Is resistance infinity? Go to Step 4. “YEL” wire shorted to
ground circuit.
4 Wire harness check
1) Measure voltage between “G51-7” terminal of HVAC
control module connector and vehicle body ground with
ignition switch turned ON.
Is voltage 0 V? Go to Step 5. “YEL” wire shorted to
other circuit.
5 Serial communication signal check
1) Connect connectors to BCM and HVAC control module.
2) Using oscilloscope, check that serial communication
signal is outputted referring to “Reference waveform
No.8” of “Inspection of BCM and its Circuits in Section
10B”.
Is serial communication signal outputted at “G37-11”
terminal of BCM connector? HVAC control module
faulty.
BCM (included in
junction block
assembly) faulty.
DTC detecting condition
Trouble area
Data received by HVAC control module from BCM is erroneous continuously. • BCM (included in junction block assembly)
• HVAC control module

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DTC Troubleshooting
DTC B1553: CAN Communication Signal MalfunctionS7RS0B7224021
DTC Detecting Condition and Trouble Area
DTC Troubleshooting
DTC B1557: Vehicle Speed Sensor Signal MalfunctionS7RS0B7224022
DTC Detecting Condition and Trouble Area
DTC TroubleshootingStep Action Yes No
1 Serial communication signal data check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Start engine and select “DATA LIST” mode on scan tool.
3) Check “Refrigerant Pressure”, “Vehicle Speed”, “Coolant Temp” and “Outside Air Temp” varies displayed on scan
tool.
Is displayed each va ries described varies in “Scan Tool
Data”? Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”.
Go to Step 2.
2 Serial communication signal check
1) Connect connectors to BCM and HVAC control module.
2) Using oscilloscope, check that serial communication
signal is outputted referring to “Reference waveform
No.8” of “Inspection of BCM and its Circuits in Section
10B”.
Is serial communication signal outputted at “G37-11”
terminal of BCM connector? HVAC control module
faulty.
BCM (included in
junction block
assembly) faulty.
DTC detecting condition
Trouble area
HVAC control module receives error code fr om BCM continuously.• CAN communication circuit
• BCM (included in junction block assembly)
•ECM
• HVAC control module
Step Action YesNo
1 DTC check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Check ECM and BCM for DTC.
Is there DTC(s)? Go to applicable DTC
diag. flow.
Substitute a known-
good HVAC control
module and recheck.
DTC detecting condition
Trouble area
HVAC control module receives error code from BCM continuously. • VSS circuit
• VSS
• HVAC control module
Step Action YesNo
1 DTC check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Check ECM for DTC.
Is there DTC P0500? Go to “DTC P0480: Fan
1 (Radiator Cooling
Fan) Control Circuit in
Section 1A”.
Substitute a known-
good HVAC control
module and recheck.

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Inspection of HVAC Control Module and Its CircuitS7RS0B7224026
HVAC control module and its circuits can be checked at HVAC control module wiring couplers by measuring voltage.
CAUTION!
HVAC control module can not be checked by itself. It is strictly prohibited to connect voltmeter to
HVAC control module with couplers disconnected from it.

Voltage Check
1) Remove HVAC control module referring to “HVAC Control Module Removal and Installation”.
2) Check voltage at each terminal.
NOTE
As each terminal voltage is affected by the battery voltage, confirm that it is 11 V or more when ignition
switch is ON.

7812910
65 431516 14 13 12 11
G52
789101920121112
65 431718 16 15 14 13
G51
1
2
I5RS0A722017-02
1. HVAC control module2. HVAC control module connector (viewed from harness side)
Terminal Wire Color CircuitNormal
Vo l ta g e Condition
G51-1 BRN/WHT Air flow control actuator
(DEF) 10 – 14 V
Ignition switch turned ON, ai
r flow control actuator is
working in operation fr om VENT to DEF position
0 – 1 V Ignition switch turned ON, except the above condition
G51-2 BRN/YEL Air flow control actuator
(FACE) 10 – 14 V
Ignition switch turned ON, ai
r flow control actuator is
working in operation fr om DEF to VENT position
0 – 1 V Ignition switch turned ON, except the above condition
G51-3 GRY/BLU Temperature control
actuator (COOL) 10 – 14 VIgnition switch turned ON, temperature control
actuator is working in ope
ration from HOT to COOL
position
0 – 1 V Ignition switch turned ON, except the above condition
G51-4 GRY/RED Temperature control
actuator (HOT) 10 – 14 VIgnition switch turned ON, temperature control
actuator is working in operation from COOL to HOT
position
0 – 1 V Ignition switch turned ON, except the above condition
G51-5 PPL/WHT Serial communication line
of data link connector 10 – 14 V Ignition switch turned ON
G51-6 — — — —
G51-7 YEL Serial communication line
of BCM Refer to “Inspection of BCM a
nd its Circuits in Section 10B”