Mazda 6. Manual - part 265

P–116

TROUBLESHOOTING (ABS/TCS/DYNAMIC STABILITY CONTROL) 

NO.9 TCS OFF LIGHT STAYS ON MORE THAN 4 SECONDS WITH IGNITION SWITCH ON

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• When performing an asterisked (*) troubleshooting inspection, shake the wiring harness and connectors while 

doing the inspection to discover whether poor contact points are the cause of any intermittent malfunction. If 
there is a problem, check to make sure connectors, terminals and wiring harnesses are connected correctly 
and undamaged.

End Of Sie

9

BRAKE system warning light stays on more than 4 seconds with ignition switch on. (Parking brake 
is released.)

[TROUBLESHOOTING HINTS]

• Warning light circuit open or shorted to ground in ABS/TCS HU/CM

1

INSPECT WIRING HARNESS BETWEEN ABS/
TCS HU/CM AND DLC-2 (DATA LINK 
CONNECTOR-2) FOR CONTINUITY AND 
SHORTS
Perform DTC inspection.
Is error message displayed regarding 
communication between ABS/TCS HU/CM and 
WDS or equivalent?

Yes

If a communication error message is displayed even after 
inspecting according to procedures displayed on WDS or 
equivalent, go to Step 7.

No

Go to next step.

2

CHECK FOR DTCS IN ABS/TCS HU/CM
Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

3

INSPECT PID/DATA IN ABS/TCS HU/CM
Inspect the following items using WDS or 
equivalent PID/DATA monitor function.

• TRAC_SW (TCS OFF switch)

Is TRAC_SW ON displayed on WDS or 
equivalent?

Yes

Go to Step 5 (TCS OFF switch system malfunction).

No

Go to next step.

*

4

CHECK FOR SHORT TO GROUND IN ABS/
TCS HU/CM
Disconnect ABS/TCS HU/CM connector.
Does TCS OFF light go out with ignition switch 
on?

Yes

Replace ABS/TCS HU/CM (short to ground in ABS/TCS 
HU/CM).

No

Inspect instrument cluster.

*

5

INSPECT TCS OFF SWITCH
Disconnect TCS OFF switch connector.
Is TRAC_SW ON displayed on WDS or 
equivalent?

Yes

Go to next step.

No

Replace TCS OFF switch (TCS will not turn off, even though 
switch is OFF).

*

6

VERIFY WHETHER MALFUNCTION IS IN 
WIRING HARNESS (BETWEEN ABS/TCS HU/
CM AND TCS OFF SWITCH FOR SHORT TO 
GROUND) OR ABS/TCS HU/CM
Is there continuity between SST connector 
terminal P and ground?

Yes

Repair wiring harness between ABS/TCS HU/CM (terminal 
P) and TCS OFF switch.

*

7

INSPECT WIRING HARNESS BETWEEN ABS/
TCS HU/CM AND DLC-2 (DATA LINK 
CONNECTOR-2) FOR SHORT TO B+
Is voltage approximately 12 V at SST 
connector terminal T?

Yes

Repair wiring harness between ABS/TCS HU/CM (terminal 
P) and data link connector.

No

Go to next step.

*

8

INSPECT WIRING HARNESS BETWEEN ABS/
TCS HU/CM AND DLC-2 (DATA LINK 
CONNECTOR-2) FOR SHORT TO GROUND
Is there continuity between SST connector 
terminal T and ground?

Yes

Repair wiring harness between ABS/TCS HU/CM and data 
link connector.

No

Replace ABS/TCS HU/CM (communication circuit 
malfunction in ABS/TCS HU/CM).

TROUBLESHOOTING (ABS/TCS/DYNAMIC STABILITY CONTROL) 

P–117

P

NO.10 TCS DOES NOT WORK CORRECTLY

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Diagnostic procedure

End Of Sie

NO.11 THERE IS MALFUNCTION IN THE SYSTEM EVEN THOUGH ABS WARNING LIGHT, BRAKE SYSTEM 
WARNING LIGHT, TCS OFF LIGHT, TCS INDICATOR LIGHT DO NOT ILLUMINTE

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Diagnostic procedure

End Of Sie

NO.1 ANY OF THE FOLLOWING LIGHTS DO NOT ILLUMINATE WITH IGNITION SWITCH ON: (ABS 
WARNING LIGHT, BRAKE SYSTEM WARNING LIGHT, DSC INDICATOR LIGHT AND/OR DSC OFF LIGHT)

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10

TCS does not work correctly.

[TROUBLESHOOTING HINTS]

• There is difference in size or air pressure between the front and rear tires.

• There is malfunction in the engine control system.

• ABS/TCS HU/CM detects TCS system malfunction.

STEP

INSPECTION

ACTION

1

CHECK TIRE SIZE AND AIR PRESSURE
Inspect tire size and air pressure.
Are size and air pressure as specified?

Yes

Go to next step.

No

Replace with specified tires or adjust tire air pressure.

2

CHECK FOR DTCS IN ABS/TCS HU/CM
Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

3

CHECK FOR DTCS IN PCM
Check the DTC for the PCM ON-BOARD 
DIAGNOSTIC SYSTEM.
Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

4

CHECK TO MAKE SURE TORQUE 
REDUCTION SIGNAL GOING FROM ABS/TCS 
HU/CM TO PCM IS BEING RECEIVED 
CORRECTLY 
Select ENG 

- 

TRQ (engine torque reduction 

signal) using WDS or equivalent.
Increase the engine speed to 3,000 rpm.
Input 280 N·m ENG 

_ 

TRQ to PCM using WDS 

or equivalent.
Does engine speed decrease?

Yes

System is normal.
Recheck customer's complaint.

No

Replace ABS/TCS HU/CM.

11

There is a malfunction in system even though ABS warning light, BRAKE system warning light, TCS 
OFF light, TCS indicator light do not illuminate.

[TROUBLESHOOTING HINTS]

• There is a difference in size or air pressure between the front and rear tires

STEP

INSPECTION

ACTION

1

CHECK FOR DTCs IN ABS/TCS HU/CM
Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

2

INSPECT ABS HYDRAULIC UNIT
Perform "ABS hydraulic unit system inspection".
Is system okay?

Yes

Inspect conventional brake system.

No

If wheels do not rotate: 
Replace ABS/TCS HU/CM.
If wheels rotate but order in which wheels rotate is 
incorrect:
Inspect brake pipe passage to ABS/TCS HU/CM.

1

Any of the following lights do not illuminate with ignition switch on: (ABS warning light, BRAKE 
system warning light, DSC indicator light and/or 

DSC

 OFF light).

[TROUBLESHOOTING HINTS]

• Check each light in the instrument cluster for malfunction.

• Poor connection at DSC HU/CM connector

• ABS warning light circuit or BRAKE system warning light circuit shorted out

(when harness is shorted out between DSC HU/CM and ABS warning light or BRAKE system warning light, each 
warning lights go off.)

• DSC indicator light circuit and/or 

DSC

 OFF light circuit may be open.

(when DSC indicator light circuit and/or 

DSC

 OFF light circuit is open, each circuit’s warning lights go off.)

P–118

TROUBLESHOOTING (ABS/TCS/DYNAMIC STABILITY CONTROL) 

Diagnostic procedure

End Of Sie

STEP

INSPECTION

ACTION

1

CHECK FOR DTCS IN DSC HU/CM

• Check the DTC for the DSC ON-BOARD 

DIAGNOSTIC SYSTEM.

• Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

2

CHECK TO SEE WHETHER MALFUNCTION 
IS IN INSTRUMENT CLUSTER SYSTEM OR 
OTHER SYSTEM

• Do other warning and indicator lights 

illuminate when IG switch is turned ON?

Yes

Go to next step.

No

Inspect or repair instrument cluster (power supply system, 
ground system).

3

VERIFY THAT DSC HU/CM CONNECTOR IS 
CONNECTED

• Is DSC HU/CM securely connected?

Yes

Go to next step.

No

Connect DSC HU/CM connector securely, then go to next 
step.

4

VERIFY THAT DSC HU/CM CONNECTOR 
TERMINAL OR RELATED CONNECTOR 
TERMINALS ARE CONNECTED

• Are DSC HU/CM connector terminal, or 

instrument cluster connector terminal, or 
related connector terminals securely 
connected?

Yes

Go to next step.

No

Connect DSC HU/CM connector terminal etc. related 
connector terminal securely.

5

CHECK TO SEE WHETHER MALUNCTION IS 
IN DSC INDICATOR LIGHT AND TCS OFF 
LIGHT OR ABS WARNING LIGHT AND 
BRAKE SYSTEM WARNING LIGHT

• If DSC indicator light and TCS OFF light do 

not illuminate, go to Step 6.

• If ABS warning light and BRAKE system 

warning light do not illuminate, go to Step 8.

-

-

6

CHECK TO SEE WHETHER MALFUNCTION 
IS IN DSC HU/CM OR OTHER

• Disconnect DSC HU/CM.

• Connect the DSC indicator light terminal and 

DSC OFF light terminal to body ground.

• Do both indicator lights illuminate with 

ignition switch on?

Yes

Replace DSC HU/CM (open in DSC HU/CM).

No

Go to next step.

7

INSPECT WIRING HARNESS BETWEEN 
INSTRUMENT CLUSTER AND DSC HU/CM 
FOR CONTINUITY

• Is there continuity between each indicator 

light terminals of instrument cluster and DSC 
HU/CM connector terminal?

Yes

Inspect or repair indicator light circuit in instrument cluster.

No

Repair malfunctioning part.

8

CHECK TO SEE WHETHER MALFUNCTION 
IS IN DSC HU/CM OR OTHER

• Disconnect DSC HU/CM and turn ignition 

switch on.

• Do ABS warning light and BRAKE system 

warning lights illuminate with ignition switch 
on?
(If above lights illuminate, both lights circuits 
are normal.)

Yes

Replace DSC HU/CM (short in DSC HU/CM).

No

Go to next step.

9

INSPECT WIRING HARNESS BETWEEN 
INSTRUMENT CLUSTER AND DSC HU/CM 
FOR SHORT

• Is there continuity between each warning 

light terminal of DSC HU/CM and ground?

Yes

Repair malfunctioning part.

No

Inspect or repair warning light circuit in instrument cluster.

TROUBLESHOOTING (ABS/TCS/DYNAMIC STABILITY CONTROL) 

P–119

P

NO.2 ANY OF THE FOLLOWING LIGHTS STAY ON: (ABS WARNING LIGHT, BRAKE SYSTEM WARNING 
LIGHT, DSC INDICATOR LIGHT AND/OR 

DSC 

OFF LIGHT)

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Diagnostic procedure

End Of Sie

2

Any of the following lights stay on: (ABS warning light, BRAKE system warning light, DSC indicator 
light and/or DSC OFF light) 

[TROUBLESHOOTING HINTS]

• Brake fluid amount is low.

• Parking brake does not release.

• No connection at DSC HU/CM connector

(when DSC HU/CM connector comes off, ABS warning light and BRAKE system warning light illuminate.)

• DSC HU/CM detected malfunction (input and output device malfunction)

• DSC HU/CM detects low voltage in power supply.

• DSC HU/CM ground malfunction

(when DSC HU/CM ground is not securely connected, ABS warning light and BRAKE system warning light 
illuminate but diagnostic trouble code does not display)

• DSC HU/CM does not operate (DSC HU/CM malfunction.)

• DSC OFF light circuit shorted in ground (when DSC OFF circuit is shorted in ground, DSC OFF light illuminated.)

• ABS warning light circuit or BRAKE system warning light circuit open

(when the harness is open between DSC HU/CM and each warning light, each warning light illuminates)

STEP

INSPECTION

ACTION

1

INSPECT BRAKE FLUID AMOUNT AND 
VERIFY THAT PARKING BRAKE RELEASES

• Is brake fluid amount normal?

• Is parking brake lever released?

Yes

Go to next step. 

No

Add brake fluid or release parking brake lever.

2

CHECK FOR DTCS IN DSC HU/CM

• Check the DTC for the DSC ON-BOARD 

DIAGNOSTIC SYSTEM.

• Have DTCs been recorded in memory?

Yes

Perform inspection using appropriate DTC.

No

Go to next step.

3

CHECK TO SEE WHETHER MALFUNCTION 
IS IN CONTROL MODULE CONNECTOR, 
TERMINAL OR OTHER

• Do ABS warning light and BRAKE system 

warning light go off after 4 seconds with 
ignition switch on?

Yes

Temporary poor connection in control module connector.
Inspect DSC HU/CM connector, then go to Step 6.
Inspect DSC HU/CM connector terminal, then go to Step 7.

No

Go to next step.

4

INSPECT BATTERY

• Is battery voltage normal?

Yes

Go to next step.

No

Inspect battery and charging system.

5

INSPECT CHARGING SYSTEM

• Is battery voltage normal with electrical load 

(A/C, headlight, etc.) on and engine idling?

Yes

Go to next step.

No

Inspect charging system (drive belt tension, generator, etc.).

6

VERIFY THAT DSC HU/CM CONNECTOR IS 
CONNECTED

• Is DSC HU/CM securely connected?

Yes

Go to next step.

No

Connect DSC HU/CM connector securely, then go to next 
step.

7

VERIFY THAT DSC HU/CM CONNECTOR 
TERMINAL OR RELATED CONNECTOR 
TERMINALS ARE CONNECTED

• Are DSC HU/CM connector terminal or 

instrument cluster connector terminal etc. 
related connector terminals securely 
connected?

Yes

Go to next step.

No

Connect DSC HU/CM connector terminal etc. related 
connector terminals securely.

8

INSPECT WIRING HARNESS BETWEEN 
INSTRUMENT CLUSTER AND DSC HU/CM 
FOR CONTINUITY

• Is there continuity between each warning 

light terminal of instrument cluster and DSC 
HU/CM connector terminal?

Yes

Go to next step.

No

Repair malfunctioning part.

9

INSPECT WIRING HARNESS BETWEEN 
INSTRUMENT CLUSTER AND DSC HU/CM 
FOR SHORT IN GROUND

• Is there continuity between each indicator 

light terminal of DSC HU/CM and ground?

Yes

Repair malfunctioning part.

No

Inspect power supply harness and ground harness of DSC 
HU/CM.
If above wiring harness are okay, replace DSC HU/CM.
If above wiring harness are malfunctioning, repair 
malfunctioning wiring harness.