ON-BOARD DIAGNOSTIC FUNCTION [CAN (CONTROLLER AREA NETWORK)]

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Block Diagram

HS-CAN

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MS-CAN

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On-Board Diagnostic Function

Malfunction 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 Unit (M-MDS display) | DTC | Malfunction location
--- | --- | ---
PCM (PCM) | U0073 | CAN system communication error
U0101 | Communication error to TCM
U0121 | Communication error to ABS HU/CM (With ABS) Communication error to DSC HU/CM (With DSC)
U0155 | Communication error to instrument cluster
TCM*1 (TCM) | U0073 | CAN system communication error
U0100 | Communication error to PCM
ABS HU/CM*2 (ABS) | U0073 | CAN system communication error
U1900 | Communication error to other module
U2023 | Abnormal message from PCM
DSC HU/CM*3 (ABS) | U0073 | CAN system communication error
U0100 | Communication error to PCM
U0101 | Communication error to TCM
U0155 | Communication error to instrument cluster
U1900 | Communication error to other module
U2023 | Abnormal message from PCM
Power retractable hardtop control module (RHT)*4 | U0073 | CAN system communication error
U0100 | Communication error to PCM
U0101 | Communication error to TCM
U2197 | Vehicle speed signal communication error
Active bonnet control module (DHS)*5 | U0001:88 | CAN system communication error
U0155:00 | Communication error to instrument cluster
Instrument cluster (IC) | U0073 | Module communication error
U0100 | Communication error to PCM
U0101 | Communication error to TCM
U0121 | Communication error to ABS HU/CM (With ABS) Communication error to DSC HU/CM (With DSC)
U0207 | Communication error to power retractable hardtop control module
U0214 | Communication error to keyless control module
U0250 | Communication error to active bonnet control module
U2023 | Abnormal message from PCM
U2197 | Signal error from PCM

*1 :AT
*2 :with ABS
*3 :with DSC
*4 :with power retractable hardtop
*5 :with active bonnet

MS-CAN

DTC Output Unit | DTC | Malfunction location
--- | --- | ---
Audio unit | 16:Er12 | Communication error between audio unit and HF/TEL unit
HF/TEL unit | 26:Er81 | CAN system communication error

Narrowing down malfunction locations

• When the CAN system is thought to be malfunctioning based on the repair order form and the malfunctioning symptom, perform the CAN system on-board diagnosis.
• DTCs are output due to a control module or sensor malfunction, or incorrect power supply. Verify the output DTCs and first inspect the DTCs not shown in the DTC table.
• The open circuit location in the CAN system can be determined by verifying the DTCs detected in each module and by the module which has failed.
• It is possible for signal error DTCs to be output in addition to communication error DTCs if there is an open circuit. Determine the open circuit location if the communication error and signal error DTCs are output simultaneously.
• For DTC details, refer to the “Self-malfunction diagnostic function”. (See Self-malfunction diagnostic function.)

Troubleshooting procedure

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Example (L.H.D.) : TCM-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 | U0101 | Communication error to TCM
DSC HU/CM | U0101 | Communication error to TCM
Power retractable hardtop control module | U0101 | Communication error to TCM

Module | Fail
--- | ---
TCM | ×

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2. A communication error DTC is displayed for the signal between the TCM and PCM/DSC HU/CM/Power retractable hardtop control module despite normal communication between the PCM and instrument cluster. In addition, a TCM failure is displayed. This indicates that there may be a malfunction in the wiring harness between the TCM and branch A, or in the TCM itself.

Example (R.H.D.) : TCM-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 | U0101 | Communication error to TCM
DSC HU/CM | U0101 | Communication error to TCM
Power retractable hardtop control module | U0101 | Communication error to TCM

Module | Fail
--- | ---
TCM | ×

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2. A communication error DTC is displayed for the signal between the TCM and PCM/DSC HU/CM/Power retractable hardtop control module despite normal communication between the PCM and instrument cluster. In addition, a TCM failure is displayed. This indicates that there may be a malfunction in the wiring harness between the TCM and branch C, or in the TCM itself.