PRECAUTION

BME040300000W03

When inspecting or servicing the ABS (ABS/TCS), note the following points:

Vehicles with ABS

1. The ABS warning light and/or BRAKE system warning light may illuminate even when the system is normal, depending on the driving conditons and details of work performed.

Warning lights that may illuminate

Cases in which the light may illuminate

Condition in which the light will go out

ABS and EBD control

• ABS warning light
• BRAKE system warning light (*1)
Under any of the following conditions:
• When the front wheels are jacked up, stuck, or placed on a chassis roller, and only the front wheel ABS wheel speed sensors are spun for more than 20 seconds.
After turning ignition switch to OFF, vehicle is driven at speed greater than 10 km/h {6.2 mph} and normal operation is confirmed.
• ABS: Cuts control.
• EBD:
1. Cuts control, in cases where the light may illuminate, only when ABS HU/CM detects that a rear wheel speed sensor is malfunctioning.
2. Wheel speed sensor determines that more than 3 wheels are functioning correctly.
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.)
• ABS warning light
• BRAKE system warning light
Battery voltage at ABS HU/CM ignition terminal Z drops below about 8.5 V. (*2)
Battery voltage rises above about 8.5 V.
(Only BRAKE system warning light goes out.)
ABS: Cuts control.
EBD: Cuts control.
• ABS warning light
Battery voltage at ABS HU/CM ignition terminal Z is below about 10 and above about 8.5 V. (*2)
Battery voltage rises above about 10 V.
ABS: Operates control.
EBD: Operates control.

*1 :
In cases where the light may illuminate, only when ABS HU/CM detects that a rear wheel's speed sensor is malfunctioning.
*2 :
If battery voltage drops below about 9 to 10 V while vehicle speed is greater than 6 km/h {3.7 mph} , ABS HU/CM records DTC B1318 (63) .

2. 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.

(1) Malfunctions in electrical system
• The ABS HU/CM has an on-board diagnostic function. With this function, the ABS warning light and/or BRAKE system 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 ON by connecting the WDS or equivalent to the DLC-2 inside the Passenger comportment. 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 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 is turned ON. In this case, drive the vehicle at a speed of more than 10km/h {6.2 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 is turned ON, 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.
• To protect the terminal, use the SST (adapter harness) (49 G066 001) when connecting the tester lead to the ABS HU/CM connector.
(2) 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 HU/CM contains delicate mechanical parts. If foreign material gets 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 material does not get inside when servicing the ABS (e.g. brake fluid replacement, pipe removal).

Vehicles with ABS/TCS

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

The ABS warning light, BRAKE system warning light, TCS indicator light and/or TCS OFF light may illuminate, even when it is normal, depending on the driving conditions and details of work performed.

Warning lights that may illuminate and/or flash

Cases in which the light may illuminate

Condition in which the light will go out

ABS and TCS control

All or any the following lights illuminate:
• ABS warning light
• BRAKE system warning light
Under any of the following conditions:
• When the front wheels are jacked up, stuck, or placed on a chassis roller, and only the front wheel ABS wheel speed sensors are spun for more than 60 seconds.
After turning ignition switch OFF, vehicle is driven at speed greater than 10 km/h {6.2 mph} and normal operation is confirmed.
• ABS: Cuts control.
• TCS: Cuts control.
• EBD:
1. Cuts control, in cases where the light may illuminate, only when ABS/TCS HU/CM detects that a wheel speed sensor determines that more than the two rear wheels are malfunctioning.
2. Operates control, if wheel speed sensor determines that more than 3 wheels are functioning correctly.
Parking brake is not fully released while driving.
Brake drags
Sudden acceleration/ deceleration.
All the following lights illuminate:
• ABS warning light
• BRAKE system warning light
Left/right or front/rear tires are different. (Size, radius, tire pressure, or wear is other than that listed on tire label.)
After turning ignition switch OFF, vehicle is driven at speed greater than 10 km/h {6.2 mph} and normal operation is confirmed.
• ABS: Cuts control.
• TCS: Cuts control.
• EBD:
1. Cuts control, in cases where the light may illuminate, only when ABS/TCS HU/CM detects that a wheel speed sensor determines that more than the two rear wheels are malfunctioning.
2. Operates control, if wheel speed sensor determines that more than 3 wheels are functioning correctly.
All the following lights illuminate:
• ABS warning light
• BRAKE system warning light
Battery voltage at ABS/TCS HU/CM ignition terminal Z drops below approx. 10 V. (*1)
Battery voltage rises above approx. 10 V.
• ABS: Operates control.
• TCS: Operates control.
• EBD: Operates control.
All the following lights illuminate:
• TCS OFF light
• TCS indicator light
When the engine coolant temperature is below 0 °C {32 °F}. (*2)
When engine is started and engine coolant temperature rises above 0 °C {32 °F}.
• ABS: Cuts control.
• EBD: Cuts control.
• TCS:
1. If TCS is operating, cuts control after gradually releasing TCS control value.
2. If TCS is not operating, cuts control.
All the following lights illuminate:
• ABS warning light
• BRAKE system warning light
When performing ABS ON-BOARD DIAGNOSTIC SYSTEM using ABS warning light while driving vehicle.
Under either of the following conditions:
• When vehicle is stopped (*3)
• When ABS ON-BOARD DIAGNOSTIC SYSTEM is released
• ABS: Operates control.
• TCS: Operates control.
• EBD: Operates control.
All the following lights flash:
• ABS warning light
• BRAKE system warning light
• TCS OFF light
When confirming DTCs or PID/DATA items using WDS or equivalent.
When ABS ON-BOARD DIAGNOSTIC SYSTEM is released.
• ABS: Cuts control.
• TCS: Cuts control.
• EBD: Cuts control.
When performing ACTIVE COMMAND MODES using WDS or equivalent.
When ABS ON-BOARD DIAGNOSTIC SYSTEM is released.
• ABS: Cuts control.
• TCS: Cuts control.
• EBD: Cuts control.

*1 :
If battery voltage drops below 10 V while vehicle speed is greater than 6 km/h {3.7 mph} , ABS/TCS HU/CM records DTC B1318 (63) .
*2 :
DTC 87 (U2021) for past malfunction is not recorded in the ABS/TCS HU/CM. DTC 87 (U2021) for present malfunction is displayed, then goes out when engine coolant temperature rises above 0 °C {32 °F} .
*3 :
When malfunctions that display DTCs occur, the ABS warning light flashes.

Warning lights that may illuminate and/or flash

Cases in which the light may illuminate

Condition in which the light will go out

ABS and TCS control

The following light illuminates:
• TCS OFF light
Until 1 second after starting the engine.
More than 1 second after starting the engine.
• ABS: Cuts control.
• TCS: Cuts control.
• EBD: Cuts control.

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.

(1) Malfunctions in electrical system
• The ABS/TCS HU/CM has an on-board diagnostic function. With this function, the ABS warning light, BRAKE system warning light, TCS indicator light, and TCS OFF light illuminate 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. Turn the ignition switch ON by connecting the WDS or equivalent to the DLC-2 inside the Passenger comportment. Approximately 5 seconds later the stored malfunctions will be displayed in the order of occurrence. To find out the causes of ABS/TCS 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/TCS 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/TCS HU/CM memory. Also, if the ABS/TCS related parts have been replaced, verify that no DTC is displayed after repairs.
• After repairing the ABS wheel-speed sensor or ABS sensor rotor, or after replacing the ABS/TCS HU/CM (ABS motor or ABS motor relay or solenoid valve), the ABS warning light, BRAKE system warning light, TCS indicator light, and/or TCS OFF light may not go off even when the ignition switch is turned to ON. In this case, drive the vehicle at a speed of more than 10 km/h {6.2 mph}, make sure the ABS warning light, BRAKE system warning light, TCS indicator light, and TCS OFF light go off, and then erase the DTC.
• When repairing, if the ABS/TCS related connectors are disconnected and the ignition switch is turned 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 switch is OFF before connecting or disconnecting the ABS/TCS HU/CM.
• To protect the terminal, use the SST (adapter harness) (49 G066 001) when connecting the tester lead to the ABS/TCS HU/CM connector.
(2) 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).