Nissan Pathfinder (2012 year). Manual - part 447

LAN-4

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

CAN COMMUNICATION SYSTEM

SYSTEM DESCRIPTION

CAN COMMUNICATION SYSTEM

System Description

INFOID:0000000007801295

• CAN communication is a multiplex communication system. This enables the system to transmit and receive

large quantities of data at high speed by connecting control units with two communication lines (CAN-H and

CAN-L).

• Control units on the CAN network transmit signals using the CAN communication control circuit. They

receive only necessary signals from other control units to operate various functions.

• CAN communication lines adopt twisted-pair line style (two lines twisted) for noise immunity.

System Diagram

INFOID:0000000007801296

Each control unit passes an electric current to the termination circuits when transmitting CAN communication

signal. The termination circuits produce an electrical potential difference between CAN-H and CAN-L. CAN

communication system transmits and receives CAN communication signals by the potential difference.

SKIB8887E

Component

Description

Main line

CAN communication line between splices

Branch line

CAN communication line between splice and a control unit

Splice

A point connecting a branch line with a main line

Termination circuit

Refer to 

LAN-5, "CAN Communication Control Circuit"

.

August 2012

2012 Pathfinder

LAN

CAN COMMUNICATION SYSTEM

LAN-5

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

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CAN Communication Control Circuit

INFOID:0000000007801297

*: These are the only control units wired with both ends of CAN communication system.

SKIB8713E

Component

System description

CAN controller

It controls CAN communication signal transmission and reception, error detection, etc.

Transceiver IC

It converts digital signal into CAN communication signal, and CAN communication signal into digital 
signal.

Noise filter

It eliminates noise of CAN communication signal.

Termination circuit

*

(Resistance of approx. 120 

Ω

)

It produces potential difference.

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2012 Pathfinder

LAN-6

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

DIAG ON CAN

DIAG ON CAN

Description

INFOID:0000000007801298

“Diag on CAN” is a diagnosis using CAN communication instead of previous DDL1 and DDL2 communication

lines, between control units and diagnosis unit.

System Diagram

INFOID:0000000007801299

SKIB8714E

Name

Harness

Description

DDL1

Tx
Rx

It is used for trouble diagnosis. (CAN-H and CAN-L are used for controlling)

DDL2

K-LINE

It is used for trouble diagnosis. (CAN-H and CAN-L are used for controlling)

Diag on CAN

CAN-H
CAN-L

It is used for trouble diagnosis and control.

August 2012

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LAN

TROUBLE DIAGNOSIS

LAN-7

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

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TROUBLE DIAGNOSIS

Condition of Error Detection

INFOID:0000000007801300

DTC (e.g. U1000 and U1001) of CAN communication is indicated on SELF-DIAG RESULTS on CONSULT if a

CAN communication signal is not transmitted or received between units for 2 seconds or more.

CAN COMMUNICATION SYSTEM ERROR

• CAN communication line open (CAN-H, CAN-L, or both)

• CAN communication line short (ground, between CAN communication lines, other harnesses)

• Error of CAN communication control circuit of the unit connected to CAN communication line

WHEN DTC OF CAN COMMUNICATION IS INDICATED EVEN THOUGH CAN COMMUNICATION
SYSTEM IS NORMAL

• Removal/installation of parts: Error may be detected when removing and installing CAN communication unit

and related parts while turning the ignition switch ON. (A DTC except for CAN communication may be

detected.)

• Fuse blown out (removed): CAN communication of the unit may cease.

• Voltage drop: Error may be detected if voltage drops due to discharged battery when turning the ignition

switch ON (Depending on the control unit which carries out CAN communication).

• Error may be detected if the power supply circuit of the control unit, which carries out CAN communication,

malfunctions (Depending on the control unit which carries out CAN communication).

• Error may be detected if reprogramming is not completed normally.

CAUTION:

CAN communication system is normal if DTC of CAN communication is indicated on SELF-DIAG

RESULTS of CONSULT under the above conditions. Erase the memory of the self-diagnosis of each

unit.

Symptom When Error Occurs in CAN Communication System

INFOID:0000000007801301

In CAN communication system, multiple units mutually transmit and receive signals. Each unit cannot transmit

and receive signals if any error occurs on CAN communication line. Under this condition, multiple control units

related to the root cause malfunction or go into fail-safe mode.

ERROR EXAMPLE

NOTE:

• Each vehicle differs in symptom of each unit under fail-safe mode and CAN communication line wiring.

• Refer to 

LAN-36, "Abbreviation List"

 for the unit abbreviation.

Example: TCM branch line open circuit

SKIB8738E

Unit name

Symptom

ECM

Engine torque limiting is affected, and shift harshness increases.

BCM

Reverse warning chime does not sound.

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2012 Pathfinder

LAN-8

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

TROUBLE DIAGNOSIS

Example: Data link connector branch line open circuit

NOTE:

• When data link connector branch line is open, transmission and reception of CAN communication signals

are not affected. Therefore, no symptoms occur. However, be sure to repair malfunctioning circuit.

• When data link connector branch line is open, “system” displayed on the CONSULT “ALL DTC” may be the

same as when the CAN communication line has short-circuit. However, symptoms differ depending on the

case. See below chart for the differences.

EPS control unit

Normal operation.

Combination meter

• Shift position indicator and OD OFF indicator turn OFF.
• Warning lamps turn ON.

ABS actuator and electric unit (control unit)

Normal operation.

TCM

No impact on operation.

IPDM E/R

Normal operation.

Unit name

Symptom

SKIB8739E

Unit name

Symptom

ECM

Normal operation.

BCM

EPS control unit

Combination meter

ABS actuator and electric unit (control unit)

TCM

IPDM E/R

“System” on the “ALL DTC”

(CONSULT)

Difference of symptom

Data link connector branch line open circuit

All Diag on CAN units are not 
indicated.

Normal operation.

CAN-H, CAN-L harness short-circuit

Most of the units which are connected to the CAN 
communication system enter fail-safe mode or are 
deactivated.

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LAN

TROUBLE DIAGNOSIS

LAN-9

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

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Example: Main Line Between Data Link Connector and ABS Actuator and Electric Unit (Control Unit) Open Circuit

Example: CAN-H, CAN-L Harness Short Circuit

SKIB8740E

Unit name

Symptom

ECM

Engine torque limiting is affected, and shift harshness increases.

BCM

• Reverse warning chime does not sound.
• The front wiper moves under continuous operation mode even though the front wip-

er switch being in the intermittent position.

EPS control unit

The steering effort increases.

Combination meter

• The shift position indicator and OD OFF indicator turn OFF.
• The speedometer is inoperative.
• The odo/trip meter stops.

ABS actuator and electric unit (control unit)

Normal operation.

TCM

No impact on operation.

IPDM E/R

When the ignition switch is ON,
• The headlamps (Lo) turn ON.
• The cooling fan continues to rotate.

SKIB8741E

August 2012

2012 Pathfinder

LAN-10

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

TROUBLE DIAGNOSIS

Self-Diagnosis

INFOID:0000000007801302

If communication signals cannot be transmitted or received among units communicating via CAN communica-

tion line, CAN communication-related DTC is displayed on the CONSULT “Self Diagnostic Result” screen.

NOTE:

The following table shows examples of CAN communication-related DTC. For other DTC, refer to the applica-

ble sections.

CAN Diagnostic Support Monitor

INFOID:0000000007801303

CONSULT and CAN diagnostic support monitor (on-board diagnosis function) are used for detecting root

cause.

MONITOR ITEM (CONSULT)

Unit name

Symptom

ECM

• Engine torque limiting is affected, and shift harshness increases.
• Engine speed drops.

BCM

• Reverse warning chime does not sound.
• The front wiper moves under continuous operation mode even though the front 

wiper switch being in the intermittent position.

• The room lamp does not turn ON.
• The engine does not start (if an error or malfunction occurs while turning the igni-

tion switch OFF.)

• The steering lock does not release (if an error or malfunction occurs while turning 

the ignition switch OFF.)

EPS control unit

The steering effort increases.

Combination meter

• The tachometer and the speedometer do not move.
• Warning lamps turn ON.
• Indicator lamps do not turn ON.

ABS actuator and electric unit (control unit)

Normal operation.

TCM

No impact on operation.

IPDM E/R

When the ignition switch is ON,
• The headlamps (Lo) turn ON.
• The cooling fan continues to rotate.

DTC

Self-diagnosis item

 (CONSULT indication)

DTC detection condition

Inspection/Action

U1000

CAN COMM CIRCUIT

ECM

When ECM is not transmitting or receiving 
CAN communication signal of OBD (emission-
related diagnosis) for 2 seconds or more.

Start the inspection. Refer 
to the applicable section 
of the indicated control 
unit.

Except 
for ECM

When a control unit (except for ECM) is not 
transmitting or receiving CAN communication 
signal for 2 seconds or more.

U1001

CAN COMM CIRCUIT

When ECM is not transmitting or receiving CAN commu-
nication signal other than OBD (emission-related diagno-
sis) for 2 seconds or more.

U1002

SYSTEM COMM

When a control unit is not transmitting or receiving CAN 
communication signal for 2 seconds or less.

U1010

CONTROL UNIT(CAN)

When an error is detected during the initial diagnosis for 
CAN controller of each control unit.

Replace the control unit 
indicating “U1010”.

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LA N

TROUBLE DIAGNOSIS

LAN-11

< SYSTEM DESCRIPTION >

[CAN FUNDAMENTAL]

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Example: CAN DIAG SUPPORT MNTR indication

Without PAST

With PAST

MONITOR ITEM (ON-BOARD DIAGNOSIS)

NOTE:

For some models, CAN communication diagnosis result is received from the vehicle monitor. (CONSULT is

not available.)

JSMIA0812GB

Item

PRESENT

Description

Initial diagnosis

OK

Normal at present

NG

Control unit error (Except for some control units)

Transmission diagnosis

OK

Normal at present

UNKWN

Unable to transmit signals for 2 seconds or more.

Diagnosis not performed

Control unit name

(Reception diagnosis)

OK

Normal at present

UNKWN

Unable to receive signals for 2 seconds or more.

Diagnosis not performed

No control unit for receiving signals. (No applicable optional parts)

Item

PRESENT

PAST

Description

Transmission di-

agnosis

OK

OK

Normal at present and in the past

1 – 39

Normal at present, but unable to transmit signals for 2 seconds or more 
in the past. (The number indicates the number of ignition switch cycles 
from OFF to ON.)

UNKWN

0

Unable to transmit signals for 2 seconds or more at present.

Control unit 

name

(Reception diag-

nosis)

OK

OK

Normal at present and in the past

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Normal at present, but unable to receive signals for 2 seconds or more 
in the past. (The number indicates the number of ignition switch cycles 
from OFF to ON.)

UNKWN

0

Unable to receive signals for 2 seconds or more at present.

Not diagnosed

–

Diagnosis not performed.

No control unit for receiving signals. (No applicable optional parts)

August 2012

2012 Pathfinder