Toyota 4Runner: Downhill Assist Control Switch Malfunction (Test Mode DTC) (C1379)

Toyota 4Runner Service Manual / Brake / Brake Control / Dynamic Control Systems / Vehicle Stability Control System(for Hydraulic Brake Booster) / Downhill Assist Control Switch Malfunction (Test Mode DTC) (C1379)

DESCRIPTION

w/ Downhill Assist Control:

DTC C1379 is cleared when the downhill assist control switch sends a downhill assist control operation signal or when test mode ends.

w/ Crawl Control:

DTC C1379 is cleared when the crawl control switch sends a crawl control operation signal or when test mode ends.

DTC Code	DTC Detection Condition	Trouble Area
C1379	Stored only during test mode.	ECU-IG NO. 1 fuse (w/ Crawl Control) ECU-B fuse (w/ Crawl Control) Downhill assist control switch (w/ Downhill Assist Control) Crawl control switch (w/ Crawl Control) Harness or connector Master cylinder solenoid (Skid control ECU)

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE

1.	CONFIRM VEHICLE SPECIFICATIONS

(a) Confirm the vehicle specifications.

Result

Result	Proceed to
w/ Downhill Assist Control	A
w/ Crawl Control	B

GO TO STEP 6

2.	READ VALUE USING TECHSTREAM (DOWNHILL ASSIST CONTROL SW)

(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.

(f) Check the Data List for proper functioning of the downhill assist control switch.

ABS/VSC/TRAC

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Downhill Assist Control SW	Downhill assist control switch / ON or OFF	ON: Downhill assist control on OFF: Downhill assist control off	-

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Downhill Assist Control SW

Downhill assist control switch / ON or OFF

ON: Downhill assist control on

OFF: Downhill assist control off

OK:

The Techstream displays ON or OFF according to downhill assist control switch operation.

GO TO STEP 4

3.	CHECK TEST MODE DTC

(a) Perform the Downhill Assist Control Switch Check in the Test Mode Procedure (See page ).

OK:

Test mode DTC C1379 is cleared.

USE SIMULATION METHOD TO CHECK

REPLACE MASTER CYLINDER SOLENOID

4.	INSPECT DOWNHILL ASSIST CONTROL SWITCH

REPLACE DOWNHILL ASSIST CONTROL SWITCH

5.	CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - DOWNHILL ASSIST CONTROL SWITCH/BODY GROUND)

(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

REPLACE MASTER CYLINDER SOLENOID

REPAIR OR REPLACE HARNESS OR CONNECTOR

6.	CHECK CAN BUS

(a) Check that there are no problems with the CAN communication system (See page ).

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

7.	READ VALUE USING TECHSTREAM (CRAWL CONTROL MODE SELECT SWITCH)

(a) Turn the ignition switch off.

(b) Connect the Techstream to the DLC3.

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / D-SEAT SW / Data List.

(f) Check the Data List for proper functioning of the crawl control mode select switch.

D-SEAT SW

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Crawl Control Main Switch	Crawl control switch (ON/OFF switch)/ ON or OFF	ON: Crawl control on OFF: Crawl control off	-

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Crawl Control Main Switch

Crawl control switch (ON/OFF switch)/ ON or OFF

ON: Crawl control on

OFF: Crawl control off

OK:

The Techstream displays ON or OFF according to crawl switch operation.

GO TO STEP 10

8.	READ VALUE USING TECHSTREAM (CRAWL CONTROL SWITCH)

(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.

(f) Check the Data List for proper functioning of the crawl control switch.

ABS/VSC/TRAC

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Crawl Control Switch	Crawl switch (mode select switch)/ LOW, MIDLOW, MID, MIDHIGH or HIGH	Actual crawl speed selector switch position	-

OK:

The Techstream displays LOW, MIDLOW, MID, MIDHIGH or HIGH according to crawl switch (mode selector switch) operation.

GO TO STEP 11

9.	CHECK TEST MODE DTC

(a) Perform the crawl switch check in the Test Mode Procedure (See page ).

OK:

Test mode DTC C1379 is cleared.

USE SIMULATION METHOD TO CHECK

REPLACE MASTER CYLINDER SOLENOID

10.	CHECK TERMINAL VOLTAGE AND RESISTANCE (IG, +B, GND)

(a) Disconnect the U1 drive monitor switch connector.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
U1-6 (+B) - Body ground	Always	11 to 14 V
U1-12 (IG) - Body ground	Ignition switch ON	11 to 14 V

Standard Resistance:

Tester Connection	Condition	Specified Condition
U1-7 (GND) - Body ground	Always	Below 1 Ω

Text in Illustration

*a	Front view of wire harness connector (to Drive Monitor Switch)

REPLACE DRIVE MONITOR SWITCH

REPAIR OR REPLACE HARNESS OR CONNECTOR

11.	REPLACE DRIVE MONITOR SWITCH

(a) Replace the drive monitor switch (See page ).

12.	CHECK TEST MODE DTC

(a) Perform the crawl switch check in the Test Mode Procedure (See page ).

OK:

Test mode DTC C1379 is cleared.

END

REPLACE MASTER CYLINDER SOLENOID

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