CAN SYSTEM DESCRIPTION

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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.

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.

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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.

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• 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.

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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).

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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
Signal	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
Immobilizer system related information	IN	―	―	―	―	―	―	OUT
Engine condition	OUT	IN	IN	IN	IN	―	IN	IN
Engine torque	OUT	IN (DSC)	―	―	―	―	―	―
Engine speed	OUT	IN (DSC)	IN	IN	―	IN	IN	IN
Vehicle speed	OUT	―	IN	IN	IN	IN	―	IN
Accelerator pedal position	OUT	IN	―	―	―	―	―	―
Brake pedal switch condition	OUT	IN	IN	―	―	―	―	―
Brake system condition	OUT	IN	IN	―	―	―	―	―
Distance travelled	OUT	―	―	―	―	―	―	IN
Selector lever position	OUT	―	IN	―	―	―	―	IN
Gear position	OUT	IN (DSC)	―	―	―	―	―	IN
Target gear position	OUT	―	―	―	―	―	―	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
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
Air bag system warning light illumination request	―	―	―	―	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
Signal	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
Immobilizer system related information	IN	―	―	―	―	―	―	OUT
Engine condition	OUT	IN	IN	IN	IN	―	IN	IN
Engine torque	OUT	IN (DSC)	―	―	―	―	―	―
Engine speed	OUT	IN (DSC)	IN	IN	―	IN	IN	IN
Vehicle speed	OUT	―	IN	IN	IN	IN	―	IN
Accelerator pedal position	OUT	IN	―	―	―	―	―	―
Accelerator pedal position	IN	―	―	―	―	―	―	OUT
Brake pedal switch condition	OUT	IN	IN	―	―	―	―	―
Brake pedal switch condition	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
Air bag system warning light illumination request	―	―	―	―	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

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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).

DTC table

DTC	Malfunction location	DTC Output Unit
U0001:88	Module communication error (HS-CAN)	• ABS HU/CM (with ABS) • DSC HU/CM (with DSC) • BCM • Keyless control module (with advanced keyless and start system) • SAS control module • EPS control module • Theft-deterrent control module (with theft-deterrent system) • Instrument cluster
U0028:87	BCM communication error	• Keyless control module (with advanced keyless and start system)
U0073:00	Module communication error (CAN bus)	• PCM
U0100:00	PCM communication error	• ABS HU/CM (with ABS) • DSC HU/CM (with DSC) • BCM • Keyless control module (with advanced keyless and start system) • EPS control module • Theft-deterrent control module (with theft-deterrent system) • Instrument cluster
U0121:00	ABS HU/CM (with ABS) or DSC HU/CM (with DSC) communication error	• PCM • BCM • EPS control module • Instrument cluster
U0126:00	EPS control module communication error	• DSC HU/CM (with DSC)
U0131:00	EPS control module communication error	• Instrument cluster
U0140:00	BCM communication error	• PCM • Theft-deterrent control module (with theft-deterrent system) • Instrument cluster
U0151:00	SAS control module communication error	• PCM • Instrument cluster
U0155:00	Instrument cluster communication error	• PCM • ABS HU/CM (with ABS) • DSC HU/CM (with DSC) • SAS control module
U0214:00	Keyless control module communication error	• Instrument cluster
U2101:00	Signal error from instrument cluster	• ABS HU/CM (with ABS) • DSC HU/CM (with DSC)

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

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Example (L.H.D.): PCM-related wiring harness open circuit (if DTC is output)

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

Module

Displayed DTC

Probable malfunction location

PCM

U0140:00

BCM communication error

U0155:00

Instrument cluster communication error

Module	Displayed DTC	Probable malfunction location
PCM	U0140:00	BCM communication error
U0155:00	Instrument cluster communication error

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2. Even though communication among the ABS HU/CM (vehicles with ABS) and SAS control module is normal, a malfunction between the PCM, BCM or BCM and the branch B wiring harness can be considered because communication error DTCs are displayed for the BCM and the instrument cluster.

Example (R.H.D.): PCM-related wiring harness open circuit (if DTC is output)

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

Module

Displayed DTC

Probable malfunction location

PCM

U0151:00

SAS control module communication error

U0155:00

Instrument cluster communication error

Module	Displayed DTC	Probable malfunction location
PCM	U0151:00	SAS control module communication error
U0155:00	Instrument cluster communication error

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2. Even though communication among the BCM and ABS HU/CM (vehicles with ABS) is normal, a malfunction between the PCM, BCM or BCM and the branch B wiring harness can be considered because communication error DTCs are displayed for the SAS control module and the instrument cluster.