ON-BOARD DIAGNOSTIC SYSTEM FUNCTION [ABS]

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Malfunction Detection Function

• The malfunction detection function detects malfunctions in the input/output signal system of the ABS HU/CM when the ignition switch is at the ON position.
• When the ABS HU/CM is started up, the following malfunction detections are performed.

  ― The ABS and brake system warning lights illuminate for approx. 3 s when the ignition switch is turned to the ON position. At the same time, the fail-safe relay is operated, and the input/output signals of each part is monitored for malfunction diagnosis. After starting to drive, the first time the vehicle speed is approx. 10 km/h {6.2 mph} or more the pump motor is operated and malfunction diagnosis is performed again.

• When malfunctions are detected, the corresponding lights are illuminated to alert the driver. Using the external tester communication function, DTCs can be output through the CAN_H and CAN_L of the DLC-2. At the same time, malfunction detection results are sent to the memory and fail-safe functions.

Memory Function

• The memory function stores DTCs of malfunctions in input/output signal systems. With this function, once a DTC is stored it is not cleared after the ignition switch has been turned LOCK position, even if the malfunctioning signal system has returned to normal.
• Since the ABS HU/CM has a built-in non-volatile memory, DTCs are not cleared even if the battery is removed. Therefore, it is necessary to clear the memory after performing repairs. Refer to the Workshop Manual for the DTC clearing procedure.

Fail-safe Function

• When the malfunction detection function determines a malfunction, each light illuminates to advise the driver. At this time, the fail-safe function controls the ABS and EBD as shown in the fail-safe function table.

  Warning
  • If EBD control is suspended the rear wheels could lock-up before the front wheels. If this occurs, the vehicle could swerve and become unstable. Therefore always inspect the system immediately if EBD control is suspended.

Fail-safe Function Malfunction Contents

Malfunction location | DTC number | Fail-safe function
--- | --- | ---
Warning light illumination status | Control status
Mazda Modular Diagnostic System (M-MDS) display | ABS warning light | Brake system warning light (when parking brake is released) | ABS control | EBD control
Power supply system | B1317 | Illuminated*1 | Illuminated*1 | Control disabled*2 | Control disabled*2
B1318
ABS HU/CM system | B1342 | Illuminated | Illuminated | Control disabled | Control disabled
Brake switch signal system | B1484 | Not illuminated | Illuminated*3 | Control enabled | Control enabled
ABS HU/CM configuration system | B2477 | Flash | Not illuminated | Control disabled | Control enabled
ABS sensor rotor | C1141 | Illuminated | Not illuminated | Control disabled | Control enabled
C1142
C1143
C1144
ABS wheel-speed sensor system | C1145
C1148
C1155
C1158
C1165
C1168
C1175
C1178
ABS wheel-speed sensor/ABS sensor rotor systems | C1233
C1234
C1235
C1236
Solenoid valve system | C1194 | Illuminated | Illuminated | Control disabled | Control disabled
C1198
C1210
C1214
C1242
C1246
C1250
C1254
Valve relay system | C1186 | Illuminated | Illuminated | Control disabled | Control disabled
C1266 | Not illuminated | Control enabled
Pump motor, motor relay systems | C1095 | Illuminated | Illuminated | Control disabled | Control enabled
C1096
Incorrect ABS HU/CM installed | C1805 | Illuminated | Illuminated | Control disabled | Control enabled
CAN communication system | U0073 | Not illuminated | Not illuminated | Control enabled | Control enabled
U1900
Abnormal message from PCM | U2023

*1 :If the ignition voltage returns to normal, the light goes out.
*2 :If the ignition voltage returns to normal, control is enabled.
*3 :Vehicles without malfunction warning light. (Applied VIN (assumed): NC18**215550—, NC18**250831—, NC30**202488—, NCA8**251024—