2009 INFINITI QX56 4WD

DLN-24
< COMPONENT DIAGNOSIS >[ATX14B]
P1802 – P1804, P1809 T
RANSFER CONTROL UNIT
P1802 – P1804, P1809 TRANSFER CONTROL UNIT
DescriptionINFOID:0000000003772084
The transfer control unit controls the transfer contro l device which controls shifts between AUTO, 4H and 4LO
and between 2WD and 4WD. A DTC may se t when any of the following occur:
 Malfunction is detected in the memory (RAM) system of transfer control unit.
 Malfunction is detected in the memory (ROM) system of transfer control unit.
 Malfunction is detected in the memory (E EPROM) system of transfer control unit.
 AD converter system of transfer control unit is malfunctioning.
DTC LogicINFOID:0000000003772085
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.DTC CONFIRMATION PROCEDURE
1. Turn ignition switch ON.
2. Perform self-diagnosis.
Are DTC's P1802 - P1804 or P1809 detected?
YES >> Perform diagnosis procedure. Refer to DLN-24, "Diagnosis Procedure".
NO >> Inspection End.
Diagnosis ProcedureINFOID:0000000003772086
1.INSPECTION START
Do you have CONSULT-III?
YES or NO
YES >> GO TO 2.
NO >> GO TO 3.
2.PERFORM SELF-DIAGNOSIS (WITH CONSULT-III)
With CONSULT-III
1. Turn ignition switch ON. (Do not start engine.)
2. Select SELF-DIAG RESULTS mode for ALL MODE AWD/4WD with CONSULT-III.
3. Touch ERASE.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Perform the self-diagnosis again.
Is the CONTROL UNIT 1 [P1802], CONTROL UNIT 2 [P1803], CONTRO L UNIT 3 [P1804] or CONTROL
UNIT 4 [P1809] displayed?
YES >> Replace transfer control unit. Refer to DLN-130, "Removal and Installation".
NO >> Inspection End.
3.PERFORM SELF-DIAGNOSIS (WITHOUT CONSULT-III)
DTC CONSULT-III Diagnostic item is detected when... Reference
[P1802] CONTROL UNIT 1 Malfunction is detected in the memory
(RAM) system of transfer control unit.
Refer to DLN-24
.
[P1803] CONTROL UNIT 2
Malfunction is detected in the memory
(ROM) system of transfer control unit.
[P1804] CONTROL UNIT 3 Malfunction is detected in the memory
(EEPROM) system of transfer control
unit.
[P1809] CONTROL UNIT 4 AD converter system of transfer control
unit is malfunctioning.
Revision: December 20092009 QX56

P1802 – P1804, P1809 TRANSFER CONTROL UNIT
DLN-25
< COMPONENT DIAGNOSIS > [ATX14B]
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DLN
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Without CONSULT-III
1. Perform the self-diagnosis and then eras e self-diagnostic results. Refer to DLN-18, "CONSULT-III Func-
tion (ALL MODE AWD/4WD)".
2. Perform the self-diagnosis again.
Do the self-diagnostic results indicate AD converter?
YES >> Replace transfer control unit. Refer to DLN-130, "Removal and Installation".
NO >> Inspection End.
Revision: December 20092009 QX56

DLN-28
< COMPONENT DIAGNOSIS >[ATX14B]
P1810 NEUTRAL-4LO SWITCH
P1810 NEUTRAL-4LO SWITCH
DescriptionINFOID:0000000003772093
The neutral-4LO switch detects that the transfer case
is in neutral or 4LO range. DTC P1810 will set when an
improper signal from the neutral-4LO switch is input due to an open or short circuit.
DTC LogicINFOID:0000000003772094
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.DTC CONFIRMATION PROCEDURE
1. Turn ignition switch ON.
2. Perform self-diagnosis.
Is DTC P1810 displayed?
YES >> Perform diagnosis procedure. Refer to DLN-28, "Diagnosis Procedure".
NO >> Inspection End.
Diagnosis ProcedureINFOID:0000000003772095
1.CHECK 4LO POSITION SWITCH SIGNAL
With CONSULT-III1. Start engine.
2. Select DATA MONITOR mode for A LL MODE AWD/4WD with CONSULT-III.
3. Read out the value of N POSI SW TF.
Without CONSULT-III
1. Start engine.
2. Check voltage between transfer control unit harness connector
terminal and ground.
DTC CONSULT-III Diagnostic item is detected when... Reference
[P1810] 4L POSI SW TF Improper signal from neutral-4LO switch
is input due to open or short circuit.Refer to
DLN-28
.
Condition Display value
 Vehicle stopped
 Engine running
 A/T selector lever N position
 Brake pedal depressed 4WD shift switch: 2WD,
AUTO or 4H
OFF
4WD shift switch: 4H to
4LO (While actuator mo-
tor is operating.) OFF
→ ON
4WD shift switch: 4LO to
4H (While actuator motor
is operating.) ON
→ OFF
4WD shift switch: 4LO ON
SDIA2693E
Revision: December 20092009 QX56

P1810 NEUTRAL-4LO SWITCHDLN-29
< COMPONENT DIAGNOSIS > [ATX14B]
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DLN
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Are inspection results normal?
YES >> GO TO 5.
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN TR ANSFER CONTROL UNIT AND NEUTRAL-4LO SWITCH
1. Turn ignition switch OFF. (Stay for at least 5 seconds.)
2. Disconnect transfer control unit harness connecto r and the neutral-4LO switch harness connector.
3. Check continuity between transfer control unit harness connec- tor E143 terminal 25 and neutral-4LO switch harness connector
F60 terminal 13.
Also check harness for short to ground and short to power.
Are inspection results normal?
YES >> GO TO 3.
NO >> Repair or replace damaged parts.
3.CHECK GROUND CIRCUIT
1. Turn ignition switch OFF. (Stay for at least 5 seconds.)
2. Disconnect neutral-4LO switch harness connector.
3. Check continuity between neutral-4LO switch harness connec- tor F60 terminal 12 and ground.
Also check harness for short to ground and short to power.
Are inspection results normal?
YES >> GO TO 4.
NO >> Repair open circuit or short to ground or short to power in harness or connectors.
4.CHECK 4LO SWITCH
1. Turn ignition switch OFF.
2. Disconnect neutral-4LO switch harness connector.
3. Remove neutral-4LO switch.
Connector Te r m i n a l
(Wire col-
or) Condition
Voltage
(Approx.)
E143 25 -
Ground  Vehicle stopped
 Engine running
 A/T selector lever
N position
 Brake pedal de- pressed 4WD shift switch:
2WD, AUTO or 4H
Battery
voltage
4WD shift switch: 4H to
4LO (While actuator
motor is operating.) Battery
voltage
→
0V
4WD shift switch: 4LO
to 4H (While actuator
motor is operating.) 0V
→
Battery
voltage
4WD shift switch: 4LO 0V
Continuity should exist.
SDIA2694E
Continuity should exist.
SDIA2695E
Revision: December 20092009 QX56

P1813 4WD SHIFT SWITCHDLN-31
< COMPONENT DIAGNOSIS > [ATX14B]
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DLN
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P1813 4WD SHIFT SWITCH
DescriptionINFOID:0000000003772097
The 4WD shift switch allows the driver to select AUTO, 2WD or 4WD and 4H or 4LO. DTC P1813 will set if
more than two switch inputs are simultaneously detected by the transfer control unit due to a short circuit in the
4WD shift switch.
DTC LogicINFOID:0000000003772098
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.DTC CONFIRMATION PROCEDURE
1. Turn ignition switch ON.
2. Perform self-diagnosis.
Is DTC P1813 displayed?
YES >> Perform diagnosis procedure. Refer to DLN-31, "Diagnosis Procedure".
NO >> Inspection End.
Diagnosis ProcedureINFOID:0000000003772099
1.CHECK 4WD SHIFT SWITCH SIGNAL
With CONSULT-III
1. Turn ignition switch ON. (Do not start engine.)
2. Select DATA MONITOR mode for ALL MODE AWD/4WD with CONSULT-III.
3. Read out ON/OFF switching action of the 2WD SWITCH, AUTO SWITCH, LOCK SWITCH, 4L SW with
operating 4WD shift switch.
Without CONSULT-III
1. Turn ignition switch ON. (Do not start engine.)
2. Check voltage between transfer control unit harness connector
terminals and ground.
Are inspection results normal?
YES >> GO TO 5.
NO >> GO TO 2.
DTC CONSULT-III Diagnostic item is detected when... Reference
[P1813] 4WD MODE SW More than two switch inputs are simulta-
neously detected due to short circuit of
4WD shift switch.Refer to
DLN-31
.
Connector Terminal Condition Voltage (Ap-
prox.)
E142 9 - ground
4WD shift switch: 2WD Battery voltage
4WD shift switch: AUTO, 4H or 4LO 0V
18 - ground 4WD shift switch: 4H Battery voltage
4WD shift switch: 2WD, AUTO or
4LO
0V
23 - ground 4WD shift switch: 4LO Battery voltage
4WD shift switch: 2WD, AUTO or 4H 0V
24 - ground 4WD shift switch: AUTO Battery voltage
4WD shift switch: 2WD, 4H or 4LO 0V
WDIA0148E
Revision: December 20092009 QX56

DLN-32
< COMPONENT DIAGNOSIS >[ATX14B]
P1813 4WD SHIFT SWITCH
2.CHECK 4WD SHIFT SWITCH POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF. (Stay for at least 5 seconds.)
2. Disconnect 4WD shift switch harness connector.
3. Check voltage between 4WD shift switch harness connector ter- minal 1 and ground.
4. Turn ignition switch ON. (Do not start engine.)
5. Check voltage between 4WD shift switch harness connector ter- minal 1 and ground.
Are inspection results normal?
YES >> GO TO 3.
NO >> Refer to DLN-22, "Diagnosis Procedure"
.
3.CHECK HARNESS BETWEEN 4WD SHIFT SWITCH AND TRANSFER CONTROL UNIT
1. Turn ignition switch OFF. (Stay for at least 5 seconds.)
2. Disconnect transfer control unit harness connector and the 4WD shift switch harness connector.
3. Check continuity between the following terminals.
- Transfer control unit harness connector E142 terminal 9 and 4WD shift switch harness connector M141 terminal 2.
- Transfer control unit harness connector E142 terminal 18 and 4WD shift switch harness connector M141 terminal 5.
- Transfer control unit harness connector E142 terminal 23 and 4WD shift switch harness connector M141 terminal 6.
- Transfer control unit harness connector E142 terminal 24 and
4WD shift switch harness connector M141 terminal 3.
Also check harness for short to ground and short to power.
Are inspection results normal?
YES >> GO TO 4.
NO >> Check the following. If any items are damaged, repair or replace damaged parts.  Harness for short or open between battery and transfer shut off relay harness connector E69
terminal 5.
 Power supply circuit for transfer control unit. Refer to DLN-22, "Diagnosis Procedure"
.
4.CHECK 4WD SHIFT SWITCH
1. Turn ignition switch OFF. (Stay for at least 5 seconds.)
2. Disconnect 4WD shift switch harness connector.
Connector Terminal Voltage (Approx.)
M141 1 - Ground 0V
SDIA2383E
Connector Terminal Voltage (Approx.) M141 1 - Ground Battery voltage
PDIA0210E
Continuity should exist.SDIA2699E
Revision: December 20092009 QX56

P1813 4WD SHIFT SWITCHDLN-33
< COMPONENT DIAGNOSIS > [ATX14B]
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DLN
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3. Operate 4WD shift switch and check continuity between 4WD shift switch terminals.
Are inspection results normal?
YES >> GO TO 5.
NO >> Replace 4WD shift switch.
5.CHECK TRANSFER CONTROL UNIT
Check transfer control unit input/output signal. Refer to DLN-81, "Reference Value"
.
Are inspection results normal?
YES >> GO TO 6.
NO >> Check transfer control unit pin terminals for damage or loose connection with harness connector.
If any items are damaged, repair or replace damaged parts.
6.CHECK DTC
Drive the vehicle and then perform self-diagnosis.
Are inspection results normal?
YES >> Inspection End.
NO >> Replace transfer control unit. Refer to DLN-130, "Removal and Installation"
.
Component InspectionINFOID:0000000003772100
COMPONENT INSPECTION
1. Turn ignition switch OFF. (Stay for at least 5 second.)
2. Disconnect 4WD shift switch harness connector.
3. Operate 4WD shift switch and check continuity between 4WD
shift switch terminals.
Terminal Condition Continuity
1 - 2 4WD shift switch: 2WD Yes
4WD shift switch: AUTO, 4H and
4LO
No
1 - 3 4WD shift switch: AUTO Yes
4WD shift switch: 2WD, 4H and
4LO
No
1 - 4 4WD shift switch: 2WD No
4WD shift switch: AUTO, 4H and
4LO
Ye s
1 - 5 4WD shift switch: 4H Yes
4WD shift switch: 2WD, AUTO,
and 4LO
No
1 - 6 4WD shift switch: 4LO Yes
4WD shift switch: 2WD, AUTO and
4H
No
WDIA0205E
Terminal Condition Continuity
1 - 2 4WD shift switch: 2WD Yes
4WD shift switch: AUTO, 4H and
4LO
No
1 - 3 4WD shift switch: AUTO Yes
4WD shift switch: 2WD, 4H and
4LO
No
WDIA0205E
Revision: December 20092009 QX56

DLN-34
< COMPONENT DIAGNOSIS >[ATX14B]
P1813 4WD SHIFT SWITCH
4. If the inspection results are abnormal replace the 4WD shift switch.
1 - 44WD shift switch: 2WD No
4WD shift switch: AUTO, 4H and
4LO
Ye s
1 - 5 4WD shift switch: 4H Yes
4WD shift switch: 2WD, AUTO,
and 4LO
No
1 - 6 4WD shift switch: 4LO Yes
4WD shift switch: 2WD, AUTO and
4H
No
Terminal Condition Continuity
Revision: December 20092009 QX56