Toyota 4Runner: Fail-safe Chart

Toyota 4Runner Service Manual / Brake / Brake Control / Dynamic Control Systems / Vehicle Stability Control System(for Hydraulic Brake Booster) / Fail-safe Chart

FAIL-SAFE CHART

1. FAIL-SAFE OPERATION

If there is a problem with sensor signals or hydraulic brake booster systems, the skid control ECU prohibits power from being supplied to the hydraulic brake booster and informs the ECM of VSC system failure.
The hydraulic brake booster turns off each solenoid and the ECM stops its VSC (traction control signal), which is based on signals from the skid control ECU. As a result, it is as if the ABS, TRAC and VSC systems are not installed in the vehicle.

ABS control is prohibited, but EBD control continues to the extent that it is possible. If EBD control is impossible, the BRAKE warning light comes on to warn the driver (See page ).
If a system component has any malfunction before control begins, operation is prohibited. If a system component has any malfunction during control, the system will gradually stop operating so as not to trigger a sudden change in vehicle conditions.
If it is impossible to control the systems, the indicator lights come on or blink to inform the driver of termination of control of the systems (See page ).

HINT:

If the hydraulic brake booster encounters a malfunction, brake performance is gradually lost and ABS, BA, TRAC, A-TRAC, AUTO LSD, VSC, downhill assist control, hill-start assist control, crawl control and multi-terrain select control system controls are prohibited.

(a) ABS, EBD and BA system:

Malfunction Area	Control Method
ABS	ABS, BA, TRAC, A-TRAC, AUTO LSD, VSC, downhill assist, hill-start assist, crawl and multi-terrain select control are prohibited
BA system	ABS, BA, TRAC, A-TRAC, AUTO LSD, VSC, downhill assist, hill-start assist, crawl and multi-terrain select control are prohibited
EBD system	ABS, BA, EBD, TRAC, A-TRAC, AUTO LSD, VSC, downhill assist, hill-start assist, crawl and multi-terrain select control are prohibited

(b) TRAC, A-TRAC, VSC, AUTO LSD, downhill assist control, hill-start assist control and crawl control system:

HINT:

The TRAC, A-TRAC, VSC, AUTO LSD, downhill assist control, hill-start assist control and crawl control systems each prohibit different controls depending on the malfunctioning part.

Malfunction Area	Control Method
Engine control system (TRAC and VSC systems)	Before control: Disables control During control: Uses only brakes to perform control
Brake control system (VSC system)	Before control: Disables control During control: Uses only engine to perform control
Brake control system (TRAC, A-TRAC, AUTO LSD, downhill assist control, hill-start assist control and crawl control systems)	Before control: Disables control During control: Disables control (by gradually ending control)

Malfunction Area

Control Method

Engine control system

(TRAC and VSC systems)

Before control: Disables control

During control: Uses only brakes to perform control

Brake control system

(VSC system)

Before control: Disables control

During control: Uses only engine to perform control

Brake control system

(TRAC, A-TRAC, AUTO LSD, downhill assist control, hill-start assist control and crawl control systems)

Before control: Disables control

During control: Disables control (by gradually ending control)

2. SYSTEM TEMPERATURE PROTECTION OPERATION

If the TRAC, A-TRAC, AUTO LSD, downhill assist control, hill-start assist control or crawl control system has been used constantly for a long time, the temperature of the hydraulic brake booster may increase excessively. If the temperature increases excessively, the skid control buzzer sounds intermittently. If the temperature increases even more, the skid control buzzer sounds for 3 seconds and the TRAC OFF indicator light comes on.

System	Indicator Condition
TRAC, A-TRAC, AUTO LSD or hill-start assist control	TRAC OFF indicator light comes on
AUTO LSD	TRAC OFF indicator light comes on AUTO LSD indicator light goes off
Downhill assist control	TRAC OFF indicator light comes on Downhill assist control indicator light blinks and then turns off
Crawl control	TRAC OFF indicator light comes on Crawl indicator light blinks and then turns off

HINT:

If the systems automatically return to normal operating conditions, the TRAC OFF indicator light goes off. As this is not a malfunction, no DTC is stored.

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