Mazda 6. Manual - part 350

ON-BOARD DIAGNOSTIC [HEADLIGHT AUTO LEVELING SYSTEM] 

T–149

T

DTC B2390

A6E816467000W05

DTC B2390

Communication system between auto leveling control unit (main) and auto leveling control unit 
(sub).

DETECTION 

CONDITION

Warning
• incorrect servicing of the auto leveling control unit could result in electrical shock because 

the unit is integrated with the discharge headlight control unit. Before servicing the auto 
leveling control unit, always refer to “Discharge headlight service warnings.” (See 

T–25 

DISCHARGE HEADLIGHT SERVICE WARNINGS

)

Communication between auto leveling control unit (main) and auto leveling control unit (sub) is not 
performed.

POSSIBLE 

CAUSE

• Auto leveling control unit (main) malfunction

• Open or shortcircuit in wiring harness between auto leveling control unit (main) and auto leveling 

control unit (sub)

T–150

ON-BOARD DIAGNOSTIC [HEADLIGHT AUTO LEVELING SYSTEM] 

Diagnostic procedure

End Of Sie

STEP

INSPECTION

ACTION

1

INSPECT CONNECTOR CONNECTION

• Check fit of auto leveling control units and 

headlight connectors on both sides (auto 
leveling control unit (main) and (sub)).

• Are installation condition and fit okay?

Yes

Go to next step.

No

After correcting fit, clear DTC and check DTC again.

• If DTC is displayed again, go to next step.

2

INSPECT HEADLIGHT (LH) AND 

HEADLIGHT (RH)

• Disconnect auto leveling control unit (main) 

connector (20-pin) and headlight (LH) 
connector (12-pin) and auto leveling control 
unit (sub) connector (20-pin) and headlight 
(RH) connector (12-pin).

• Is there continuity between the following 

connectors?
— Auto leveling control unit (main) connector 

(terminal I) and headlight (LH) connector 
(terminal 1F)

— Auto leveling control unit (sub) connector 

(terminal P) and headlight (RH) connector 
(terminal 1F)

Yes

Go to next step.

No

Possible cause is an open circuit in headlight. Replace 
headlight (LH) or headlight (RH). (See 

T–26 FRONT 

COMBINATION LIGHT REMOVAL/INSTALLATION

)

3

INSPECT WIRING HARNESS BETWEEN 

HEADLIGHT (LH) CONNECTOR AND 
HEADLIGHT (RH) CONNECTOR

• Disconnect headlight (LH) connector (12-pin) 

and headlight (RH) connector (12-pin).

• Is there continuity between the following 

connectors?
—  Headlight (LH) connector (terminal 1F) 

and headlight (RH) connector (terminal 
1F)

Yes

Repair auto leveling control unit (main).
(See 

T–30 DISCHARGE HEADLIGHT CONTROL UNIT 

REMOVAL/INSTALLATION

)

No

Repair or replace wiring harness between headlight (LH) 
and headlight (RH).

ON-BOARD DIAGNOSTIC [HEADLIGHT AUTO LEVELING SYSTEM] 

T–151

T

DTC B2607

A6E816467000W06

Remark: In this case other DTCs can be reported for wrong side.

DTC B2607

Auto leveling control unit controlling system.

DETECTION 

CONDITION

Warning
• incorrect servicing of the auto leveling control unit could result in electrical shock because 

the unit is integrated with the discharge headlight control unit. Before servicing the auto 
leveling control unit, always refer to “Discharge headlight service warnings.” (See 

T–25 

DISCHARGE HEADLIGHT SERVICE WARNINGS

)

Operation of auto leveling control unit (main) and auto leveling control unit (sub) are reversed.

POSSIBLE 

CAUSE

• Mounting of auto leveling control unit (main) and auto leveling control unit (sub) changed

• Poor fit of auto leveling control unit

• Headlight malfunction

• Open or short circuit in wiring harness between auto leveling sensors and headlight (LH)

T–152

ON-BOARD DIAGNOSTIC [HEADLIGHT AUTO LEVELING SYSTEM] 

Diagnostic procedure for headlight (LH)

Diagnostic procedure for headlight (RH)

End Of Sie

STEP

INSPECTION

ACTION

1

INSPECT CONNECTION

• Check fit of auto leveling control unit and fit 

of connectors.

• Is fit okay?.

Yes

Go to next step.

No

After correcting fit, clear DTC and check DTC again.

• If DTC is displayed again, go to next step.

2

INSPECT WIRING HARNESS BETWEEN 

AUTO LEVELING SENSOR 
CONNECTORS AND HEADLIGHT 
(LH) CONNECTOR

• Disconnect front and rear auto leveling 

sensor connector (6-pin) and headlight (LH) 
connector (4-pin).

• Is there no continuity between the following 

connectors?
— Headlight (LH) connector (terminal 2C) 

and front auto leveling sensor connector 
(terminal A)

— Headlight (LH) connector (terminal 2D) 

and front auto leveling sensor connector 
(terminal D)

Yes

Go to next step.

No

Repair or replace wiring harness between front auto leveling 
sensor and headlight (LH).

3

INSPECT HEADLIGHT (LH)

• Disconnect auto leveling control unit (main) 

connector (20-pin) and headlight (LH) 
connector (4-pin).

• Is there no continuity between the following 

connectors?
— Headlight (LH) connector (terminal 2B) 

and auto leveling control unit (main) 
connector (terminal H)

— Headlight (LH) connector (terminal 2A) 

and auto leveling control unit (main) 
connector (terminal F)

Yes

Clear DTC and check DTC again.

• If DTC is displayed again, replace auto leveling control 

unit. 
(See 

T–30 DISCHARGE HEADLIGHT CONTROL UNIT 

REMOVAL/INSTALLATION

)

No

Replace headlight (LH). (See 

T–26 FRONT COMBINATION 

LIGHT REMOVAL/INSTALLATION

)

STEP

INSPECTION

ACTION

1

INSPECT CONNECTION

• Check fit of auto leveling control unit.

• Is fit okay?.

Yes

Go to next step.

No

After correcting fit, clear DTC and check DTC again.

• If DTC is displayed again, go to next step.

2

INSPECT HEADLIGHT (RH)

• Disconnect auto leveling control unit (sub) 

connector (20-pin).

• Is there no continuity between the following 

connectors?
— Terminals F and K

Yes

Clear DTC and check DTC again.

• If DTC is displayed again, replace auto leveling control 

unit. 
(See 

T–30 DISCHARGE HEADLIGHT CONTROL UNIT 

REMOVAL/INSTALLATION

)

No

Replace headlight (LH). (See 

T–26 FRONT COMBINATION 

LIGHT REMOVAL/INSTALLATION

)