Toyota 4Runner: Downhill Assist Control Indicator Light does not Come ON

Toyota 4Runner Service Manual / Brake / Brake Control / Dynamic Control Systems / Vehicle Stability Control System(for Hydraulic Brake Booster) / Downhill Assist Control Indicator Light does not Come ON

DESCRIPTION

Even if the downhill assist control switch is pressed, the downhill assist control indicator light blinks and downhill assist control does not activate under the following conditions:

The transfer is in H4.
The brake system is malfunctioning.
The temperature of the hydraulic brake booster increases and downhill assist control is temporarily canceled.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the master cylinder solenoid, perform calibration (See page ).

PROCEDURE

1.	CHECK CAN COMMUNICATION LINE

(a) Turn the ignition switch off.

(b) Connect the Techstream to the DLC3.

(d) Turn the Techstream on.

(e) Select CAN Bus Check from the System Selection Menu screen and follow the prompts on the screen to inspect the CAN bus (See page ).

OK:

CAN Bus Check indicates no malfunctions in CAN communication.

GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

2.	CHECK FOR DTC

(a) Check for DTCs (See page ).

Result

Result	Proceed to
DTC is not output	A
DTC is output	B

REPAIR CIRCUITS INDICATED BY OUTPUT DTCS

3.	INSPECT DOWNHILL ASSIST CONTROL SWITCH

(a) Remove the downhill assist control switch (See page ).

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
1 (E) - 4 (+B2)	Not pushed in	10 kΩ or higher
1 (E) - 4 (+B2)	Pushed in	Below 1 Ω

Text in Illustration

*a	Component without harness connected (Downhill Assist Control Switch)

REPLACE DOWNHILL ASSIST CONTROL SWITCH

4.	CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU HDCS CIRCUIT)

(a) Disconnect the A6 skid control ECU connector.

(b) Disconnect the U4 downhill assist control switch connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A6-44 (HDCS) - U4-4 (+B2)	Always	Below 1 Ω
A6-44 (HDCS) - Body ground	Always	10 kΩ or higher
U4-1 (E) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	READ VALUE USING TECHSTREAM (DOWNHILL ASSIST CONTROL LIGHT)

(a) Turn the ignition switch off.

(b) Connect the Techstream to the DLC3.

(d) Turn the Techstream on.

(e) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

ABS/VSC/TRAC

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Downhill Assist Control Light	Downhill assist control indicator light/ ON or OFF	ON: Indicator light on OFF: Indicator light off	-

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Downhill Assist Control Light

Downhill assist control indicator light/ ON or OFF

ON: Indicator light on

OFF: Indicator light off

(f) When performing the Downhill Assist Control Light Active Test, check Downhill Assist Control Light in the Data List (See page
).

ABS/VSC/TRAC

Tester Display	Test Part	Control Range	Diagnostic Note
Downhill Assist Control Light	Downhill assist control indicator light	Indicator light ON/OFF	Observe the combination meter.

Result

Result		Proceed to
Data List Display	Data List Display when Performing Active Test ON/OFF Operation	Proceed to
ON	Does not change between ON and OFF	A
ON	Changes between ON and OFF	B
OFF	Does not change between ON and OFF	A
OFF	Changes between ON and OFF	B

REPLACE MASTER CYLINDER SOLENOID

GO TO METER / GAUGE SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

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