Infiniti G37 Coupe. Manual - part 1259

C1900, C1901, C1906, C1907, C1927, C1933 4WAS MAIN CONTROL UNIT

STC-87

< COMPONENT DIAGNOSIS >

[WITH 4WAS]

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C1900, C1901, C1906, C1907, C1927, C1933 4WAS MAIN CONTROL UNIT

Description

INFOID:0000000001666388

• 4WAS rear actuator and the power steering solenoid valve is controlled by each sensor signal.
• The fail-safe functions stops the rear wheel angle function (the front wheel is the steering wheel cutting

angle) when the electric components and the mechanical components are malfunctioning.

• The protective function stops 4WAS system temporarily when the input signal is not inputted to 4WAS main

control unit (When battery-power dose not work temporarily).

• 4WAS front control unit and 4WAS main control unit perform two-way transmitting/receiving signals for opti-

mal control of 4WAS system via 4WAS communication line.

DTC Logic

INFOID:0000000001666389

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

RECHECK DTC

With CONSULT-III

1.

Turn the ignition switch from OFF to ON.

2.

Perform 4WAS main control unit self-diagnosis.

Is DTC “C1900”, “C1901”, “C1906”, “C1907”, “C1927” or “C1933” detected?

YES

>> Proceed to diagnosis procedure. Refer to 

STC-87, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000001666390

1.

PERFORM SELF-DIAGNOSIS (4WAS MAIN CONTROL UNIT)

With CONSULT-III

Perform 4WAS main control unit self-diagnosis.
Is any DTC “C1900”, “C1901”, “C1906”, “C1907”, “C1927” or “C1933” detected?

YES

>> Replace 4WAS main control unit. Refer to 

STC-178, "Exploded View"

.

NO

>> GO TO 2.

2.

CHECK INFORMATION

With CONSULT-III

Check the “DATA MONITOR” value of each DTC detected with the self-diagnosis function. Refer to 

STC-155,

"Reference Value"

.

Is each data the standard value?

YES

>> Check each harness connector pin terminal for disconnection.

DTC

Items

(CONSULT-III screen terms)

Diagnostic item is detected when...

Possible cause

C1900

CONTROL UNIT
[ABNORMAL1]

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

C1901

CONTROL UNIT
[ABNORMAL2]

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

C1906

CONTROL UNIT
[ABNORMAL5]

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

C1907

CONTROL UNIT
[ABNORMAL4]

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

C1927

CONTROL UNIT
[ABNORMAL5]

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

C1933

CONTROL UNIT

An error is detected inside 4WAS main control unit.

4WAS main control unit 
error

STC-88

< COMPONENT DIAGNOSIS >

[WITH 4WAS]

C1900, C1901, C1906, C1907, C1927, C1933 4WAS MAIN CONTROL UNIT

NO

>> Replace 4WAS main control unit. Refer to 

STC-178, "Exploded View"

.

Special Repair Requirement

INFOID:0000000001666391

BEFORE REPLACING 4WAS MAIN CONTROL UNIT

• Record the self-diagnosis results (history).

CAUTION:

• Never erase the memory (history) of self-diagnosis results when replacing 4WAS main control unit

after diagnosis.

• Erase the memory of the self-diagnosis results (record) after printing out or recording all the val-

ues of “DATA MONITOR”.

C1902, C1903, C1904, C1910, C1913 4WAS REAR MOTOR OUTPUT

STC-89

< COMPONENT DIAGNOSIS >

[WITH 4WAS]

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C1902, C1903, C1904, C1910, C1913 4WAS REAR MOTOR OUTPUT

Description

INFOID:0000000001666392

• 4WAS rear motor activates 4WAS rear actuator.
• Maintain the toe-stiffness of rear wheels against the road external force because the irreversible sufficiency

performance hypoid gear is used.

DTC Logic

INFOID:0000000001666393

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

RECHECK DTC

With CONSULT-III

1.

Perform “SELF DIAGNOSTIC MODE” item on “ACTIVE TEST” of 4WAS main control unit.

CAUTION:

Perform the active test while stopping the vehicle.

2.

Perform 4WAS main control unit self-diagnosis.

Is DTC “C1902”, “C1903”, “C1904”, “C1910” or “C1913” detected?

YES

>> Proceed to diagnosis procedure. Refer to 

STC-89, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000001666394

1.

CHECK 4WAS REAR MOTOR CIRCUIT

1.

Turn the ignition switch OFF.

2.

Disconnect 4WAS main control unit harness connector.

3.

Disconnect 4WAS rear motor harness connector.

4.

Check the continuity between 4WAS main control unit harness connector and 4WAS rear motor harness
connector.

DTC

Items

(CONSULT-III screen terms)

Diagnostic item is detected when...

Possible cause

C1902

MOTOR OUTPUT
[REV CURRENT]

4WAS rear motor current error is detected.
(4WAS rear motor current output direction differs.)

4WAS rear motor error

C1903

MOTOR OUTPUT
[NO CURRENT]

4WAS rear motor current error is detected.
(Current is input to 4WAS main control unit if 4WAS 
main control unit output is “OFF”.)

4WAS rear motor error

C1904

MOTOR OUTPUT
[OVERCURRENT]

4WAS rear motor current error is detected.
(4WAS rear motor output is overcurrent.)

4WAS rear motor error

C1910

MOTOR OUTPUT
[MOTOR LOCK]

4WAS rear motor inside error is detected.
(4WAS rear motor does not move or the rear wheel an-
gle sensor does not change if 4WAS main control unit 
output is 14A or more.)

4WAS rear motor error

C1913

MOTOR OUTPUT
[ABNORML SIG]

4WAS rear motor current error is detected.
(4WAS rear motor does not move or the rear wheel an-
gle sensor output does not change when 4WAS main 
control unit output is 18A or more, and 4WAS main mo-
tor output is low.)

4WAS rear motor error

4WAS main control unit

4WAS rear motor

Continuity

Connector

Terminal

Connector

Terminal

B54

38

B36

1

Existed

39

2

STC-90

< COMPONENT DIAGNOSIS >

[WITH 4WAS]

C1902, C1903, C1904, C1910, C1913 4WAS REAR MOTOR OUTPUT

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Repair or replace the harnesses and connectors.

2.

CHECK 4WAS REAR MOTOR

Check the continuity between 4WAS rear motor connector terminals.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>>  Replace 4WAS rear actuator. Refer to 

STC-180, "Exploded View"

.

3.

PERFORM ACTIVE TEST (4WAS MAIN CONTROL UNIT)

With CONSULT-III

1.

Connect 4WAS main control unit harness connector.

2.

Connect 4WAS rear motor harness connector.

3.

Perform “SELF DIAGNOSTIC MODE” item on “ACTIVE TEST” of 4WAS main control unit.

CAUTION:

Perform the active test while vehicle is stopped.

4.

Check “MOTOR VOLTAGE”, “MOTOR CURRENT” and “MTR CRNT OPE” while performing the active
test.

Is “MONITOR” the standard value?

YES

>> GO TO 4.

NO

>>  Replace 4WAS rear actuator. Refer to 

STC-180, "Exploded View"

.

4.

PERFORM SELF-DIAGNOSIS (4WAS MAIN CONTROL UNIT)

With CONSULT-III

Perform 4WAS main control unit self-diagnosis.

Is any DTC “C1902”, “C1903”, “C1904”, “C1910” or “C1913” detected?

YES

>> Replace 4WAS main control unit. Refer to 

STC-178, "Exploded View"

.

NO

>> GO TO 5.

5.

CHECK INFORMATION

With CONSULT-III

Check the “DATA MONITOR” value of each DTC detected with the self-diagnosis function. Refer to 

STC-155,

"Reference Value"

.

Is each data the standard value?

YES

>> Check each harness connector pin terminal for disconnection.

NO

>> Replace 4WAS main control unit. Refer to 

STC-178, "Exploded View"

.

Component Inspection (4WAS Rear Motor)

INFOID:0000000001666395

1.

CHECK 4WAS REAR MOTOR

1.

Turn the ignition switch OFF.

2.

Disconnect 4WAS main control unit harness connector and 4WAS rear motor harness connector.

3.

Check the continuity between 4WAS rear motor connector terminals.

4WAS rear motor

Continuity

Connector

Terminal

B36

1 – 2

Existed

Monitor item

Condition

Display value

MOTOR VOLTAGE

Ignition switch: ON

Battery voltage

MOTOR CURRENT

4WAS rear motor running

0 – 20 A

MTR CRNT OPE

4WAS rear actuator neutral condition 
and vehicle straight-ahead position

Approx. 

−

2 – 2 A

4WAS rear motor running

Approx. 

−

20 – 20 A