ON-BOARD DIAGNOSTIC OUTLINE

ON-BOARD DIAGNOSTIC OUTLINESM1934993

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• The on-board diagnostic function allows for detecting malfunctions in the input/output signals when the ignition key is at the ON position.

• The DLC-2, which combines the failure detection and detection maintenance connectors, has been adopted to improve serviceability. By connecting a Mazda Modular Diagnostic System (M-MDS) to the DLC-2, malfunction diagnosis can be carried out.

• Using a Mazda Modular Diagnostic System (M-MDS) DTCs can be retrieved or erased, depending on the screen display, thus improving serviceability.

Block Diagram

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Self-diagnostic Function

Failure detection function

• The failure detection function detects malfunctions in the input/output signal systems of the 4WD CM and displays them when the ignition key is at the ON position.

• When the ignition key is turned to the ON position, the 4WD CM system begins operation, and the 4WD warning light illuminates for 3 seconds while the function checks for open circuits. At the same time the function monitors the condition of the power supply voltage and checks for internal malfunctions.

• Then, once the system is running, the function checks the operating conditions of the 4WD solenoid and the differential oil temperature sensor at regular intervals to determine whether there is any malfunction.

• If any malfunction is detected during these diagnostic tests, the warning light illuminates according to the malfunction to alert the driver. Also, a DTC is output to DLC-2 via the CAN line. Also, at the same time the failure detection result is sent to the memory and fail-safe functions.

Memory function

• This function stores DTCs for malfunctions of the input/output signal systems as determined by the failure detection function. Once a DTC is stored, it is not cleared even if the input/output signal system malfunction returns to normal when the ignition key is turned to the LOCK position (engine OFF).

• Since DTCs are stored in the non-volatile memory inside the 4WD CM, they are not cleared even if the battery is disconnected. Therefore, it is necessary to clear the memory when maintenance has been completed. For clearing DTCs, refer to the procedures in the Workshop Manual.

Fail-safe function

• When the failure detection function determines that there is a malfunction, the 4WD warning light illuminates to alert the driver. At this time, the fail-safe function suspends control or takes other measures to ensure that driving stability is not lost.

X:Available

DTC	Malfunction location	4WD warning light condition	DTC stored in memory	Control condition
P1887	4WD solenoid circuit	Illuminated	X	Stop
P1888	Differential oil temperature sensor circuit	Illuminated	X	Stop
U0073	CAN system communication error	Illuminated	X	Stop
U0100	Communication error to PCM	Illuminated	X	Stop
U0101	Communication error to TCM	Illuminated	X	Stop
U0121	Communication error to DSC HU/CM	Illuminated ^*1	X	Stop ^*2
U0155	Communication error to instrument cluster	Illuminated	X	Stop

*1:Does not illuminate when only the coupling torque request signal from the DSC HU/CM cannot be received.

*2:Only integrated DSC control is prohibited when only the coupling torque request signal from the DSC HU/CM cannot be received.

External Tester Communication Function

• This function allows for the storing and clearing of DTCs due to a communication link between the 4WD CM and an external tester.