Precaution [ABS/TCS]

PRECAUTION [ABS/TCS]

1. The ABS warning light and/or brake system warning light and/or TCS indicator light and/or TCS OFF light illuminate even when the system is normal.






*1
In cases where the light may illuminate, only when ABS/TCS HU/CM detects that a rear wheel's speed sensor is malfunctioning.
*2
If battery voltage drops below 10 V while vehicle speed is greater than 3 km/h {2 mph}, ABS/TCS HU/CM records DTC U3003:16.





2. Precautions during servicing of ABS/TCS.
The ABS/TCS is composed of electrical and mechanical parts.It is necessary to categorize malfunctions as being either electrical or hydraulic when performing troubleshooting.
a. Malfunctions in electrical system

- The ABS/TCS HU/CM has an on-board diagnostic function. With this function, the ABS warning light and/or brake system warning light and/or TCS indicator light and/or TCS OFF light will come on when there is a problem in the electrical system. Also, past and present malfunctions are recorded in the ABS/TCS HU/CM. This function can find malfunctions that do not occur during periodic inspections. Connect the M-MDS to the DLC-2. The stored malfunction will be displayed in the order of occurrence. To find out the causes of ABS/TCS malfunction, 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/TCS HU/CM usually operates normally. Be careful when searching for the cause of malfunction.
- After repair, it is necessary to clear the DTC from the ABS/TCS HU/CM memory. Also, if the ABS/TCS 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/TCS HU/CM, the ABS warning light may not go off (*) even when the ignition is switched to ON. In this case, drive the vehicle at a speed of more than 10 km/h {6.2 mph}, make sure that ABS warning light goes off, and then clear the DTC.
* The brake system warning light also illuminates when any rear wheel deformations.
- When repairing, if the ABS/TCS related connectors are disconnected and the ignition is switched to ON, the ABS/TCS HU/CM will mistakenly detect a fault and record it as a malfunction.
- To protect the ABS/TCS HU/CM, make sure the ignition is off before connecting or disconnecting the ABS/TCS HU/CM connector.

b. 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/TCS HU/CM 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).