CAN SYSTEM DESCRIPTION

id094000101000


Mechanism of CAN System-Related Module

•  A CAN system-related module is composed of an electrical circuit, CPU, and input/output interface.
•  The size of the module has been reduced due to the elimination of the bulky, superfluous, input/output interface in the conventional type of electrical module.
•  The CPU (multiplex block) controls all signals exchanged on the CAN harness.
•  Communication with non-multiplex parts is carried out by conventional input/output interface.
•  The functions of each component are shown below.

Component

Function
Electrical circuit
Supplies power to CPU and vicinity, and to input/output interface.
CPU
Computation processing block
Control function has been expanded, and when transmission is necessary, transmitted data is stored in a multiplex block. If a multiplex block receives a request to read stored data, transmitted data is read from the multiplex block.
Multiplex block
Transmits data received from bus line to computation processing block. In addition, sends transmitted data stored from computation processing block to bus line.
Input/Output interface
Electrically converts information signals from switches to, be input to CPU, and signals output from CPU for operating actuator or indicator lights.

am2zzn00000582

Twisted Pair

•  The multichannel use two spirally twisted wires called a twisted pair, and each wire, CAN_L and CAN_H, has its own special function.
am2zzn00000583
•  Both bus lines are opposite phase voltage. This allows for minimal noise being emitted and makes if difficult for noise interference to be received.

Time Division Multiplex

•  For information exchange between electrical modules in a conventional system, a wire connection was necessary for each information signal. However, by sending the different signal at varying times over one channel, it is possible to send a large amount of information via a small harness.
•  In the conventional, non-multiplex system, in order to control the illumination of the five bulbs, one switch and one channel was necessary for each bulb. For bulbs B and C to illuminate, switches B and C must be ON and electricity must flow through the channel. With the time multiplex system, this can be done through one channel. The channel is comprised of five data signal transmitters which transmit either a “0” or “1” signal to indicate whether a bulb turns ON or OFF. For example, to illuminate bulbs B and C, transmitters B and C transmit a “1” and transmitters A, D, and E transmit a “0”. When the receiver receives these signal, bulbs B and C illuminate.
am2zzn00000584

Vehicle CAN System

•  By rearranging the multiple signal, common information between the CAN system-related modules is transmitted and received through the multichannel.
•  The signal transmitted by one CAN system-related module is sent through the multichannel to all the CAN system-related modules, but only the concerned module (s) receives the signal and performs the appropriate operation (ex. light illumination, fan operation).
am2zzn00000594

CAN signal table

•  Signals transmitted using the CAN system are as follows:

HS-CAN (ZJ, ZY)

OUT: Output (sends signal)
IN: Input (receives signal)

Signal

Multiplex module

PCM

ABS HU/CM (with ABS), DSC HU/CM (with DSC)

TCM

(CVT)

BCM

Keyless control module (with advanced keyless entry and start system)

SAS control module

Theft-deterrent control module (with theft-deterrent system)

EPS control module

Instrument cluster
Immobilizer system related information
OUT
―
―
―
IN
―
―
―
IN
IN
―
―
―
―
―
―
―
OUT
Engine condition
OUT
IN
―
IN
IN
IN
―
IN
IN
Engine torque
OUT
IN
(DSC)
―
―
―
―
―
―
―
OUT
―
IN
―
―
―
―
―
―
Target engine torque
IN
―
OUT
―
―
―
―
―
―
Engine status at idle
OUT
―
IN
―
―
―
―
―
―
Engine speed
OUT
IN
(DSC)
―
IN
IN
―
IN
IN
IN
OUT
―
IN
―
―
―
―
―
―
Vehicle speed
OUT
―
―
IN
IN
IN
IN
―
IN
IN
―
OUT
―
―
―
―
―
―
Accelerator pedal position
OUT
IN
(DSC)
IN
―
―
―
―
―
―
Brake pedal position
OUT
―
IN
―
―
―
―
―
―
Brake pedal switch condition
OUT
IN
―
IN
―
―
―
―
―
Brake system condition
OUT
IN
―
IN
―
―
―
―
―
Distance travelled
OUT
―
―
―
―
―
―
―
IN
Torque converter status
IN
―
OUT
―
―
―
―
―
―
IN
―
OUT
―
―
―
―
―
IN
―
―
OUT
―
―
―
―
―
IN
Torque converter rotation ratio
IN
―
OUT
―
―
―
―
―
―
Selector lever position
OUT
―
IN
IN
―
―
―
―
IN
Gear position
OUT
IN
(DSC)
―
―
―
―
―
―
IN
IN
―
OUT
IN
―
―
―
―
IN
IN
―
OUT
―
―
―
―
―
IN
―
―
OUT
―
―
―
―
―
IN
―
―
OUT
IN
―
―
―
―
―
Target gear position
IN
―
OUT
―
―
―
―
―
IN
Throttle position
OUT
―
IN
―
―
―
―
―
―
Target gear position
OUT
―
―
―
―
―
―
―
IN
Tire size
OUT
IN
―
―
―
―
―
―
―
Fuel cut request
IN
―
OUT
―
―
―
―
―
―
CVT system-related information
IN
―
OUT
―
―
―
―
―
―
Cruise control system-related information
OUT
―
IN
―
―
―
―
―
―
MIL illumination request
OUT
―
IN
―
―
―
―
―
IN
IN
―
OUT
―
―
―
―
―
―
Fuel injection amount
OUT
―
―
―
―
―
―
―
IN
Engine coolant temperature
OUT
―
IN
―
―
―
―
―
IN
Generator warning light illumination request
OUT
―
―
―
―
―
―
―
IN
Cruise control illumination request
OUT
―
―
―
―
―
―
―
IN
Wheel speed (LF, RF, LR, RR)
IN
OUT
IN
IN
―
―
―
―
―
Brake system status
IN
OUT
IN
―
―
―
―
―
―
Brake system warning light illumination request
―
OUT
―
―
―
―
―
―
IN
ABS status
IN
OUT
IN
―
―
―
―
―
―
ABS condition
IN
OUT
IN
―
―
―
―
―
―
ABS warning light illumination request
―
OUT
―
―
―
―
―
―
IN
Door/liftgate opening and closing
―
―
―
OUT
―
―
IN
―
IN
Door lock-link switch condition
―
―
―
OUT
―
―
IN
―
IN
Key reminder switch condition
―
―
―
OUT
―
―
―
―
IN
Key cylinder switch condition
―
―
―
OUT
―
―
IN
―
―
Turn indicator light illumination request
―
―
―
OUT
―
―
―
―
IN
Liftgate opener condition
―
―
―
OUT
―
―
IN
―
―
High beam illumination request
―
―
―
OUT
―
―
―
―
IN
Front fog light condition
―
―
―
OUT
―
―
―
―
IN
Rear fog light condition
―
―
―
OUT
―
―
―
―
IN
Running light condition
IN
―
―
OUT
―
―
―
―
IN
Parking brake position
―
―
―
OUT
―
―
―
―
IN
Brake fluid level
―
―
―
OUT
―
―
―
―
IN
TNS relay condition
IN
―
―
OUT
―
―
―
―
IN
Oil pressure switch condition
―
―
―
OUT
―
―
―
―
IN
Front wiper switch condition
IN
―
―
OUT
―
―
―
―
―
Running light condition
IN
―
―
OUT
―
―
―
―
IN
Keyless warning buzzer operation request
―
―
―
―
OUT
―
―
―
IN
Keyless indicator light illumination request
―
―
―
―
OUT
―
―
―
IN
Keyless warning light illumination request
―
―
―
―
OUT
―
―
―
IN
Buckle switch condition (driver-side)
―
―
―
IN
―
OUT
―
―
IN
Buckle switch condition (passenger-side)
―
―
―
―
―
OUT
―
―
IN
Air bag system warning buzzer condition
―
―
―
―
―
OUT
―
―
IN
Air bag system warning light illumination request
―
―
―
―
―
OUT
―
―
IN
―
IN
OUT
Steering angle/steering angle sensor condition
―
IN
(DSC)
―
―
―
―
―
OUT
―
EPS condition
―
―
―
―
―
―
―
OUT
IN

HS-CAN (MZ-CD 1.4 DI Turbo, MZ-CD 1.6 (Y6))

OUT: Output (sends signal)
IN: Input (receives signal)

Signal

Multiplex module

PCM

ABS HU/CM (with ABS), DSC HU/CM (with DSC)

BCM

Keyless control module (with advanced keyless entry and start system)

SAS control module

Theft-deterrent control module (with theft-deterrent system)

EPS control module

Instrument cluster
Immobilizer system related information
OUT
―
―
IN
―
―
―
IN
IN
―
OUT
Engine condition
OUT
IN
IN
IN
IN
―
IN
IN
Engine torque
OUT
IN
(DSC)
―
―
―
―
―
―
OUT
―
IN
―
―
―
―
―
Engine speed
OUT
IN
(DSC)
IN
IN
―
IN
IN
IN
Vehicle speed
OUT
―
IN
IN
IN
IN
―
IN
Accelerator pedal position
OUT
IN
―
―
―
―
―
―
IN
―
―
―
―
―
―
OUT
Brake pedal switch condition
OUT
IN
IN
―
―
―
―
―
IN
―
―
―
―
―
―
OUT
Brake system condition
OUT
IN
IN
―
―
―
―
―
Distance travelled
OUT
―
―
―
―
―
―
IN
Gear position
OUT
IN
(DSC)
―
―
―
―
―
IN
Tire size
OUT
IN
―
―
―
―
―
―
MIL illumination request
OUT
―
―
―
―
―
―
IN
Fuel injection amount
OUT
―
―
―
―
―
―
IN
Engine coolant temperature
OUT
―
―
―
―
―
―
IN
Generator warning light illumination request
OUT
―
―
―
―
―
―
IN
Cruise control illumination request
OUT
―
―
―
―
―
―
IN
Wheel speed (LF, RF, LR, RR)
IN
OUT
IN
―
―
―
―
―
Brake system warning light illumination request
―
OUT
―
―
―
―
―
IN
ABS condition
IN
OUT
―
―
―
―
―
―
ABS warning light illumination request
―
OUT
―
―
―
―
―
IN
ABS torque data type
IN
OUT
―
―
―
―
―
―
Door/liftgate opening and closing
―
―
OUT
―
―
IN
―
IN
Door lock-link switch condition
―
―
OUT
―
―
IN
―
IN
Key reminder switch condition
―
―
OUT
―
―
―
―
IN
Key cylinder switch condition
―
―
OUT
―
―
IN
―
―
Turn indicator light illumination request
―
―
OUT
―
―
―
―
IN
Liftgate opener condition
―
―
OUT
―
―
IN
―
―
High beam illumination request
―
―
OUT
―
―
―
―
IN
Front fog light condition
―
―
OUT
―
―
―
―
IN
Rear fog light condition
―
―
OUT
―
―
―
―
IN
Running light condition
IN
―
OUT
―
―
―
―
IN
Parking brake position
―
―
OUT
―
―
―
―
IN
Brake fluid level
―
―
OUT
―
―
―
―
IN
Oil pressure switch condition
―
―
OUT
―
―
―
―
IN
Keyless warning buzzer operation request
―
―
―
OUT
―
―
―
IN
Keyless indicator light illumination request
―
―
―
OUT
―
―
―
IN
Keyless warning light illumination request
―
―
―
OUT
―
―
―
IN
Buckle switch condition (driver-side)
―
―
IN
―
OUT
―
―
IN
Buckle switch condition (passenger-side)
―
―
―
―
OUT
―
―
IN
Air bag system warning buzzer condition
―
―
―
―
OUT
―
―
IN
Air bag system warning light illumination request
―
―
―
―
OUT
―
―
IN
IN
OUT
Steering angle/steering angle sensor condition
―
IN
(DSC)
―
―
―
―
OUT
―
EPS condition
―
―
―
―
―
―
OUT
IN
Clutch pedal switch condition
IN
―
―
―
―
―
―
OUT


On-board Diagnostic System Outline

•  The CAN system related module has an on-board diagnostic function. In case a malfunction occurs, the malfunctioning part can be determined.
•  The on-board diagnostic function consists of the following functions: a malfunction detection function, which detects malfunctions in the CAN system-related parts; a memory function, which stores detected DTCs; a display function, which indicates malfunctioning areas and status via DTC display.
•  Using the Mazda Modular Diagnostic System (M-MDS), DTCs can be read out and deleted.
•  A fail-safe function is equipped in case a malfunction occurs in the CAN system. The sending module sends an error signal and the receiving module illuminates a warning light to ensure safety.

On-board Diagnostic System Construction and Operation


Block Diagram

am2zzn00001345


Failure detection function

•  The failure detection function in each CAN system-related module detects malfunctions in input/output signals.
•  This function outputs the DTC for the detected malfunction to the DLC-2, and also sends the detected result to the memory function and fail-safe function.


Fail-safe function

•  When the failure detection function determines that there is a malfunction, the fail-safe function illuminates a warning light to inform the driver of the malfunction.


Memory function

•  The memory function stores the DTC for the malfunction of input/output signals for related parts, as determined by the failure detection function.


Self-malfunction diagnostic function

•  The self-malfunction diagnostic function determines that there is a malfunction, and outputs a signal, as a DTC, to the DLC-2. The DTC can be read out using the Mazda Modular Diagnostic System (M-MDS).

HS-CAN

DTC output module

DTC

Malfunction location
PCM (ZJ, ZY)
U0073:00
CAN system communication error
U0101:00
Communication error to TCM
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
U0140:00
Communication error to BCM
U0151:00
Communication error to SAS control module
U0155:00
Communication error to instrument cluster
PCM (MZ-CD 1.4 DI Turbo)
U0073:00
CAN system communication error
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
U0140:00
Communication error to BCM
U0155
Communication error to instrument cluster
U0416
Communication error to EPS control module
U0423
Abnormal message from instrument cluster
PCM (MZ-CD 1.6 (Y6))
U0001:00
CAN system communication error
U0073:00
CAN system communication error
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
U0122:86
U0122:87
U0155:00
U0167:00
Communication error to instrument cluster
U0300:87
•  Communication error to keyless control module (vehicles with advanced keyless and start system)
•  Communication error to instrument cluster (vehicles with keyless entry system)
ABS HU/CM*1
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0155:00
Communication error to instrument cluster
U2101:00
Abnormal message from instrument cluster
DSC HU/CM*2
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0126:00
Communication error to EPS control module
U0155:00
Communication error to instrument cluster
U2101:00
Abnormal message from instrument cluster
BCM
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0101:00
Communication error to TCM
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
TCM*3
U0073:00
CAN system communication error
U0100:00
Communication error to PCM
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
Keyless control module*4
U0001:88
CAN system communication error
U0028:87
Communication error to BCM
U0100:00
Communication error to PCM
SAS control module
U0001:88
CAN system communication error
U0155:00
Communication error to instrument cluster
EPS control module
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
Theft-deterrent control module*5
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0140:00
Communication error to BCM
Instrument cluster
U0001:88
CAN system communication error
U0100:00
Communication error to PCM
U0101:00
Communication error to TCM
U0121:00
•  Communication error to ABS HU/CM (with ABS)
•  Communication error to DSC HU/CM (with DSC)
U0131:00
Communication error to EPS control module
U0140:00
Communication error to BCM
U0151:00
Communication error to SAS control module
U0214:00
Communication error to keyless control module

*1  :With ABS
*2  :With DSC
*3  :CVT
*4  :With advanced keyless entry and start system
*5  :With theft-deterrent system


Narrowing down malfunction locations

•  The on-board diagnostic function, by verifying the detected DTC information from each module, can narrow down a CAN system malfunction location. Refer to the self-malfunction diagnostic function for detailed information regarding DTCs. (See Self-malfunction diagnostic function.)

Flowchart

am2zzn00001346


Example (L.H.D. (ZJ, ZY)): DSC HU/CM-related wiring harness open circuit (if DTC is output)

1.  Verify the CAN system-related module DTCs and the failed module using the Mazda Modular Diagnostic System (M-MDS).

Module

Displayed DTC

Probable malfunction location
PCM (PCM)
U0121:00
Communication error to DSC HU/CM
BCM (BCM)
U0121:00
Communication error to DSC HU/CM
EPS (EPS control module)
U0121:00
Communication error to DSC HU/CM
IC (Instrument cluster)
U0121:00
Communication error to DSC HU/CM

Module

Fail
ABS (DSC HU/CM)
×

am2zzn00001354

2.  Despite normal communication between the PCM and instrument cluster, a communication error DTC is displayed for the signal between the DSC HU/CM and PCM / BCM / EPS control module / instrument cluster. In addition, the wiring harness between the DSC HU/CM and branch A is considered to be malfunctioning because “Fail” is displayed for the DSC HU/CM.


Example (R.H.D. (ZJ, ZY)): DSC HU/CM-related wiring harness open circuit (if DTC is output)

1.  Verify the CAN system-related module DTCs and the failed module using the Mazda Modular Diagnostic System (M-MDS).

Module

Displayed DTC

Probable malfunction location
PCM (PCM)
U0121:00
Communication error to DSC HU/CM
BCM (BCM)
U0121:00
Communication error to DSC HU/CM
EPS (EPS control module)
U0121:00
Communication error to DSC HU/CM
IC (Instrument cluster)
U0121:00
Communication error to DSC HU/CM

Module

Fail
ABS (DSC HU/CM)
×

am2zzn00001355

2.  Despite normal communication between the PCM and instrument cluster, a communication error DTC is displayed for the signal between the DSC HU/CM and PCM / BCM / EPS control module / instrument cluster. In addition, the wiring harness between the DSC HU/CM and branch A is considered to be malfunctioning because “Fail” is displayed for the DSC HU/CM.