Nissan Sentra manuals

Nissan Sentra Service Manual: System description

System

Can communication system

Can communication system : system description

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring.

Each control unit transmits/receives data but selectively reads required data only.

Diag on can

Diag on can : system description

System diagram


Description


Description

“Diag on CAN” is a diagnosis method which uses the CAN communication line for the communication between the control unit and the diagnostic tool.

Trouble diagnosis

Component description


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 Circuit connected across the CAN communication system. (Resistor)

Condition of error detection

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

When dtc of can communication is indicated even though can communication system is normal

Note:

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 control unit.

Symptom when error occurs in can communication system

In CAN communication system, multiple control units mutually transmit and receive signals. Each control 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 control unit under fail-safe mode and can communication line wiring.

Example: main line between data link connector and abs actuator and electric unit (control unit) open circuit


Unit name

Major symptom

ECM Engine torque limiting is affected, and shift harshness increases.
Bcm
  • Reverse warning buzzer does not sound.
  • The front wiper moves under continuous operation mode even though the front wiper 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.

Example: tcm branch line open circuit


Unit name

Major symptom

Ecm Engine torque limiting is affected, and shift harshness increases.
BCM Reverse warning buzzer does not sound.
Eps control unit Normal operation.
Combination meter
  • Shift position indicator and o/d 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.

Note:

The model (all control units on CAN communication system are Diag on CAN) cannot perform CAN diagnosis with CONSULT if the following error occurs. The error is judged by the symptom.

Error

Difference of symptom

Data link connector branch line open circuit Normal operation.
Can-h, can-l harness short-circuit Most of the control units which are connected to the can communication system enter fail-safe mode or are deactivated.

Example: data link connector branch line open circuit


Note:


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.

Example: can-h, can-l harness short circuit


Can diagnosis with consult


Can diagnosis with consult

Can diagnosis on consult extracts the root cause by receiving the following information.

Self-diagnosis

If communication signals cannot be transmitted or received among control units communicating via CAN communication 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 applicable sections.

Can diagnostic support monitor


Can diagnostic support monitor

Monitor item (consult)

Example: can diag support mntr indication

Without past


Without past


With past


With past

How to use can communication signal chart


How to use can communication signal chart

The can communication signal chart lists the signals transmitted/received among control units. It is useful for detecting the root cause by finding a signal related to the symptom, and by checking transmission and reception unit.

Basic inspection


Precaution
Precautions for Trouble Diagnosis Caution: Follow the instructions listed below. Failure to do this may cause damage to parts: Never apply 7.0 V or more to the measurement terminal. Use a t ...

Basic inspection
Diagnosis and repair workflow Trouble diagnosis flow chart Trouble diagnosis procedure Interview with customer Interview with the customer is important to detect the root cause of can commu ...

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