Mazda CX 7. Manual - part 339

ON-BOARD DIAGNOSTIC [MULTIPLEX COMMUNICATION SYSTEM]

09-02D–13

09-02D

Climate Control Unit

Note

• There is no DTC in the climate control unit that determines signal quality between it and the information 

display. Due to this, determine the malfunction location using the DTC on the information display.

1. Inspect the display of DTC U0155 using the M-MDS. (See 09-02D-7 DTC TABLE[MULTIPLEX 

COMMUNICATION SYSTEM].)

2. Referring to the following table, determine the malfunctioning part of the CAN system.

×: Normal

— : Communication error

Car- navigation Unit/Audio Unit (Base Module)

Note

• There is no DTC in the car-navigation unit/audio unit (base module) that determines signal quality 

between it and the information display. Due to this, determine the malfunction location using the DTC on 
the information display.

1. Referring to the following table, determine the malfunctioning part of the CAN system.

×: Normal

— : Communication error

Information display

1. Inspect the display of DTC U0166, U0181 and/or U0184 using the input/output check mode. (See 09-22-15 

INFORMATION DISPLAY INPUT/OUTPUT CHECK MODE.)

2. Referring to the following table, determine the malfunctioning part of the CAN system.

×: Normal

— : Communication error

Module

Communication status

Malfunction location

Instrument cluster

Information display

Climate control 
unit

— — 

• Wiring harness O

• Climate control unit

— 

×

• Wiring harness N

• Instrument cluster

×

— 

• Wiring harness Q

• Wiring harness S

• Information display

Module

Communication status

Malfunction location

Information display

Car-navigation unit
Audio unit (base module)

— 

• Wiring harness P

• Wiring harness Q

• Wiring harness S

• Car-navigation unit

• Audio unit (base module)

• Information display

Module

Communication status

Malfunction location

Climate control unit

Car-navigation unit

Audio unit (base module)

Instrument cluster

Information 
display

— — — 

• Wiring harness Q

• Wiring harness S

• Information display

— 

×

×

• Wiring harness O

• Climate control unit

×

— 

×

• Wiring harness P

• Car-navigation unit

• Audio unit (base 

module)

×

×

— 

• Wiring harness N

• Instrument cluster

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ON-BOARD DIAGNOSTIC [MULTIPLEX COMMUNICATION SYSTEM]

09-02D–14

Repair Procedure

1. Inspect the connector of malfunctioning module.

• If there is any malfunction, repair or replace the connector.

2. Inspect the malfunctioning wiring harnesses as follow: 

• If there is any malfunction, repair or replace the wiring harnesses.

• If there is no malfunction, replace the malfunctioning module.

— Short to GND

— Short to power supply

— Twisted pair short each other

— Open circuit

3. Make sure to reconnect all disconnected connectors.
4. Clear the CAN system related DTCs using the M-MDS.
5. Verify if the CAN system related DTCs are displayed using the M-MDS.

• If the same following DTCs are present, replace the malfunctioning module.

— U0073 (PCM, TCM, DSC HU/CM, AWD control module, BCM, SAS control module, keyless control 

module, instrument cluster)

— U0516 (Climate control unit)

— U2516 (Instrument cluster, information display)

— 16:Er12 (Audio unit (base module))

• If other DTC is present, perform the appropriate DTC inspection. (See 09-02D-7 DTC TABLE[MULTIPLEX 

COMMUNICATION SYSTEM].)

End Of Sie

DTC U0073[MULTIPLEX COMMUNICATION SYSTEM]

id0902e6824800

DTC

U0073

PCM
TCM
DSC HU/CM
AWD control module
BCM
SAS control module
Keyless control module
Instrument cluster

CAN system communication error

DETECTION 

CONDITION

Warning
• Detection conditions are for understanding the DTC outline before performing an inspection. 

Performing an inspection according to only detection conditions may cause injury due to 
operating error, or damage the system. When performing an inspection, always follow the 
inspection procedure.

• CAN system related harness malfunction

• Related module communication error

POSSIBLE 

CAUSE

• Open or short circuit in wiring harness

• Malfunction of connectors between PCM, TCM, DSC HU/CM, AWD control module, BCM, SAS control 

module, keyless control module, instrument cluster

• PCM malfunction

• TCM malfunction

• DSC HU/CM malfunction

• AWD control module malfunction

• BCM malfunction

• SAS control module malfunction

• Keyless control module malfunction

• Instrument cluster malfunction

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ON-BOARD DIAGNOSTIC [MULTIPLEX COMMUNICATION SYSTEM]

09-02D–15

09-02D

Diagnostic procedure

End Of Sie

STEP

INSPECTION

ACTION

1

INSPECT CAN SYSTEM-RELATED DTC

• Are any DTCs other than the following 

displayed?
— U0073

Yes

Determine malfunctioning part in CAN system.
 (See 09-02D-8 PROCEDURES FOR DETERMINING THE 
LOCATION OF A MALFUNCTION[MULTIPLEX 
COMMUNICATION SYSTEM])

No

Go to the next step.

2

INSPECT CONNECTOR

• Inspect the connector of the module that 

outputs the DTC.

• Is it normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 4.

3

INSPECT WIRING HARNESSES

• Inspect for the following malfunctioning 

wiring harnesses: 

— Short to GND

— Short to power supply

— Twisted pair short each other

— Open circuit

• Is there any malfunction?

Yes

Repair or replace the wiring harness, then go to the next 
step.

No

Go to the next step.

4

VERIFY TROUBLESHOOTING COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear the DTC using the M-MDS.

• Is the same DTC present?

Yes

Replace the module that outputs the DTC, then retry this 
step.

No

Troubleshooting completed.

DTC

U0073

PCM
TCM
DSC HU/CM
AWD control module
BCM
SAS control module
Keyless control module
Instrument cluster

CAN system communication error

F

E

2R

2T

3X

3W

5L

5I

DLC-2

1AI

1AM

3X

3W

G

H

PCM

TCM

BCM

BCM

X

W

DSC HU/CM

KEYLESS 
CONTROL 
MODULE

2E

2F

SAS 
CONTROL 
MODULE

AWD 
CNTROL 
MODULE

A14

A6

INSTRUMENT 
CLUSTER

FRONT HARNESS

EMISSION HARNESS

INSTRUMENT PANEL 
HARNESS

: 

: 

CAN_H

CAN_L

REAR HARNESS

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ON-BOARD DIAGNOSTIC [MULTIPLEX COMMUNICATION SYSTEM]

09-02D–16

DTC U0516, U2516, 16:Er12[MULTIPLEX COMMUNICATION SYSTEM]

id0902e6837100

Diagnostic procedure

End Of Sie

DTC

U0516

Climate control unit

CAN system communication error

U2516

Information display
Instrument cluster

16:Er12

Audio unit (base 
module)

DETECTION 

CONDITION

Warning
• Detection conditions are for understanding the DTC outline before performing an inspection. 

Performing an inspection according to only detection conditions may cause injury due to 
operating error, or damage the system. When performing an inspection, always follow the 
inspection procedure.

• CAN system related harness malfunction

• Related module communication error

POSSIBLE 

CAUSE

• Open or short circuit in wiring harness

• Malfunction of connectors between information display, audio unit (base module), climate control unit 

and instrument cluster

• Climate control unit malfunction

• Information display malfunction

• Audio unit (base module) malfunction

• Instrument cluster malfunction

STEP

INSPECTION

ACTION

1

INSPECT CAN SYSTEM-RELATED DTC

• Are any DTCs other than the following 

displayed?
— U0516

— U2516

— 16:Er12

Yes

Determine malfunctioning part in CAN system.
 (See 09-02D-8 PROCEDURES FOR DETERMINING THE 
LOCATION OF A MALFUNCTION[MULTIPLEX 
COMMUNICATION SYSTEM].)

No

Go to the next step.

2

INSPECT CONNECTOR

• Inspect the connector of the module that 

outputs the DTC.

• Is it normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 4.

3

INSPECT WIRING HARNESSES

• Inspect for the following malfunctioning 

wiring harnesses: 
— Short to GND

— Short to power supply

— Twisted pair short each other

— Open circuit

• Is there any malfunction?

Yes

Repair or replace the wiring harness, then go to the next 
step.

No

Go to the next step.

4

VERIFY TROUBLESHOOTING COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear the DTC using the M-MDS.

• Is the same DTC present?

Yes

Replace the module that outputs the DTC, then retry this 
step.

No

Troubleshooting completed.

: 

: 

2X

2V

B

A

L

K

2O

2P

1O

1Q

CAN_H

CAN_L

DLC-2

J

I

INSTRUMENT 
CLUSTER

CLIMATE 
CONTROL UNIT

AUDIO 
AMPLIFIER

INFORMATION 
DISPLAY

AUDIO UNIT 
(BASE MODULE)

INSTRUMENT PANEL 
HARNESS

REAR HARNESS

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