Infiniti M35/M45 Y50. Manual - part 272

INTELLIGENT KEY SYSTEM/ENGINE START FUNCTION

BL-157

C

D

E

F

G

H

J

K

L

M

A

B

BL

4. 

CHECK HARNESS CONTINUITY 2

1.

Turn ignition switch OFF.

2.

Disconnect Intelligent Key unit and steering lock unit connector.

3.

Check continuity between Intelligent Key unit connector and steering lock unit connector.

4.

Check continuity between Intelligent Key unit connector and
ground.

OK or NG

OK

>> Check the condition of harness and connector. If it is OK, check the self-diagnosis results using

CONSULT-II again.

NG

>> Repair or replace harness.

DTC B2551 STEERING LOCK UNIT

NIS001YO

DIAGNOSIS DESCRIPTION

Though the communication between the Intelligent Key unit and the steering lock unit is normal, when the
steering lock/unlock is not normal, B2551 steering lock unit malfunction judges that it is the malfunction and
displays the DTC (Diagnostic Trouble Code)

TERMINALS AND REFERENCE VALUE
Intelligent Key Unit

A

B

Continuity 

Intelligent Key 
unit connector

Terminal

 Steering lock unit 

connector

Terminal

M32

16

 M35

4

Yes

A

Ground

Continuity 

Intelligent Key unit 

connector

Terminal

M32

16

No

PIIB6226E

Termi-

nal 

No.

Wire 

color

Item

Condition

Voltage (V)

(Approx.)

Push-

button 

ignition 

switch 

position

Operation or conditions

69

O

Steering lock unit con-
dition signal-1

LOCK

Steering lock: Lock

0

ACC

Steering lock: Unlock

Battery voltage

ON

Battery voltage

70

L/Y

Steering lock unit con-
dition signal-2

LOCK

Steering lock: Lock

Battery voltage

ACC

Steering lock: Unlock

0

ON

0

71

LG

PDU signal

LOCK

Steering lock: Lock

Battery voltage

ACC

Steering lock: Unlocked moment

0

BL-158

INTELLIGENT KEY SYSTEM/ENGINE START FUNCTION

PDU (Power Distribution Unit)

SELF-DIAGNOSTIC LOGIC

DIAGNOSTIC PROCEDURE

1. 

CHECK STEERING LOCK SIGNAL

Check voltage between power distribution unit connector and ground.

OK or NG

OK

>> GO TO 2.

NG

>> GO TO 4.

Ter-

minal 

No.

Wire 

color

Item

Condition

Voltage (V)

(Approx.)

Push-

button 

ignition 

switch 

position

Operation or conditions

3

GR

Steering lock unit 
power source

LOCK

Push-button ignition switch is pressed 
under the condition that Intelligent Key is 
in the vehicle or Intelligent Key is inserted

0 

→

 Battery voltage 

→

 0

—

Any condition other than above

0

7

LG

Steering lock control 
signal-2

—

Push-button ignition switch is pressed 
under the condition that Intelligent Key is 
in the vehicle or Intelligent Key is inserted

Battery voltage

LOCK

Power supply position is in LOCK posi-
tion
(Steering lock activated)

Battery voltage 

→

 0

 

→

 Battery voltage

(Battery voltage is detected when 

activating the steering lock)

DTC

Self-diagnosis name

DTC detecting condition

Possible causes

B2551

STEERING LOCK 
UNIT

Though the communication between the 
Intelligent Key and the steering lock unit 
is normal, the steering lock unit condition 
signal is NG

●

Harness and connector
(Open or shorted in the circuit between the 
units)

●

Steering lock unit

Terminals

Condition

Voltage (V)

(Approx.)

(+)

(–)

 Power distribu-

tion unit connector

Terminal

M30

6

Ground

When turn ignition 
switch to START 
with Intelligent Key 
in the car

Battery voltage

7

6

When turn ignition 
switch to OFF 
(steering lock 
operates) 

Battery voltage

↓

0

↓

Battery voltage

7

PIIB6227E

INTELLIGENT KEY SYSTEM/ENGINE START FUNCTION

BL-159

C

D

E

F

G

H

J

K

L

M

A

B

BL

2. 

CHECK POWER DISTRIBUTION UNIT POWER SUPPLY

Check voltage between power distribution unit connector and ground.

OK or NG

OK

>> GO TO 3.

NG

>> Check if "B2558 PDU" is displayed on self-diagnosis results. If it is displayed, first perform the

diagnosis.

3. 

CHECK POWER SUPPLY CIRCUIT

1.

Turn ignition switch OFF.

2.

Disconnect power distribution unit and steering lock unit connector.

3.

Check continuity between power distribution unit connector and steering lock unit connector.

4.

Check continuity between power distribution unit connector and
ground.

OK or NG

OK

>> GO TO 5.

NG

>> Repair or replace harness.

Terminals

Condition

Voltage (V)

(Approx.)

(+)

(–)

Power distribution 

unit connector

Terminal

M30

3

Ground

When turn ignition 
switch to OFF 
(steering lock oper-
ates)

Battery voltage

↓

0

↓

Battery voltage

Ignition switch OFF

0

PIIB6228E

A

B

Continuity 

 Power distribution 

unit connector

Terminal

 Steering lock unit 

connector

Terminal

M30

3

M35

1

Yes

A

Ground

Continuity 

 Power distribution 

unit connector

Terminal

M30

3

No

PIIB6229E

BL-160

INTELLIGENT KEY SYSTEM/ENGINE START FUNCTION

4. 

CHECK COMMUNICATION CIRCUIT 1 

1.

Turn ignition switch OFF.

2.

Disconnect Intelligent Key unit and power distribution unit connector.

3.

Check continuity between Intelligent Key unit connector and power distribution unit connector.

4.

Check continuity between Intelligent Key unit connector and
ground.

OK or NG

OK

>> Check the condition of harness and connector.

NG

>> Repair or replace harness.

5. 

CHECK SIGNAL CIRCUIT

1.

Connect steering lock unit and power distribution unit connector.

2.

Check continuity between steering lock unit connector and ground.

OK or NG

OK

>> Replace steering lock unit.

NG

>> GO TO 6.

A

B

Continuity 

Intelligent Key 
unit connector

Terminal

Power distribution 

unit connector

Terminal

M33

46

M30

6

Yes

71

7

A

Ground

Continuity 

Intelligent Key 
unit connector

Terminal

M33

46

No

71

PIIB6230E

Terminals

Condition

Voltage (V)

(Approx.)

(+)

(–)

 Steering lock 

unit connector

Terminal 

M35

3

Ground

When turn igni-
tion switch to 
START with 
Intelligent Key 
in the car

Battery voltage

8

0

3

Ignition switch: 

OFF

0

8

Battery  voltage

PIIB6231E