Symptom Troubleshooting [Brakes): Precaution

When inspecting or servicing the ABS, note the following points:

The ABS warning light illuminates even when the system is normal.

ABS WARNING LIGHT ILLUMINATES CONDITIONS

Cases

Remedy

ABS control when warning light illuminates

Under the following conditions:
When the rear wheels are jacked up, stuck, or placed on a chassis roller, and only the rear wheels' ABS wheel speed sensors are spun for more than 20 seconds at more than 12 km/h {7.4 mph} .

After turning ignition switch (engine switch) off, vehicle is driven at speed greater than 12 km/h {7.4 mph} and normal operation is confirmed.

If ABS is operating, stop control after operation. If ABS is not operating, stop control immediately.

Parking brake is not fully released while driving.

Brake drag.

Sudden acceleration/deceleration.

Left/right or front/rear tires are different. (Size, radius, tire pressure, or wear is other than that listed on tire label.)

Battery voltage at ABS HU/CM ignition terminal Z drops below about 10 V.( ⁽¹⁾ )

Battery voltage rises above about 10 V .

Stop control.

Battery voltage at ABS HU/CM ignition terminal Z rises above about 17 V.( ⁽²⁾ )

Battery voltage drops below about 17 V .

⁽¹⁾	If battery voltage drops below about 10 V while vehicle speed is greater than 6 km/h {3.7 mph} , ABS HU/CM records DTC B1318 (DTC 63) .

⁽²⁾	If battery voltage rises above about 17 V while vehicle speed is greater than 6 km/h {3.7 mph} , ABS HU/CM records DTC B1318 (DTC 63) .

Precautions during servicing of ABS
The ABS is composed of electrical and mechanical parts. It is necessary to categorize malfunctions as being either electrical or hydraulic when performing troubleshooting.
- Malfunctions in electrical system
  - The ABS control module (ABS HU/CM) has an on-board diagnostic function. With this function, the ABS warning light will come on when there is a problem in the electrical system. Also, past and present malfunctions are recorded in the ABS HU/CM. This function can find malfunctions that do not occur during periodic inspections. Turn the ignition switch (engine switch) to ON position, shorting the TBS terminal and the GND terminal of the data link connector, or connecting the WDS or equivalent, and approximately 5 seconds later the stored malfunctions will be displayed in the order of occurrence. To find out the causes of ABS malfunctions, use these on-board diagnostic results.
  - If a malfunction occurred in the past but is now normal, the cause is likely a temporary poor connection of the harness. The ABS HU/CM usually operates normally. Be careful when searching for the cause of malfunction.
  - After repair, it is necessary to erase the DTC from the ABS HU/CM memory. Also, if the ABS related parts have been replaced, verify that the no DTC has been displayed after repairs.
  - After repairing the ABS wheel-speed sensor or ABS sensor rotor, or after replacing the ABS HU/CM (ABS motor or ABS motor relay or solenoid valve), the ABS warning light may not go off even when the ignition switch (engine switch) is turned to ON position. In this case, drive the vehicle at a speed of more than 12 km/h {7.4 mph} , make sure the ABS warning light goes off, and then erase the DTC.
  - When repairing, if the ABS related connectors are disconnected and the ignition switch (engine switch) is turned to ON position, the ABS HU/CM will mistakenly detect a fault and record it as a malfunction.
  - To protect the ABS HU/CM, make sure the ignition is off before connecting or disconnecting the ABS HU/CM connector.
- Malfunctions in hydraulic system
  - Symptoms in a hydraulic system malfunction are similar to those in a conventional brake malfunction. However, it is necessary to determine if the malfunction is in an ABS component or the conventional brake system.
  - The ABS hydraulic unit contains delicate mechanical parts. If foreign materials get into the component, the ABS may fail to operate. Also, it will likely become extremely difficult to find the location of the malfunction in the event that the brakes operate but the ABS does not. Make sure foreign materials do not get inside when servicing the ABS (e.g. brake fluid replacement, pipe removal).