Last Modified: 11-29-2007 1.6 C
Service Category: Suspension Section: Suspension Control System
Model Year: 2008 Model: Sequoia Doc ID: RM000001N9C00AX
Title: SUSPENSION CONTROL: AIR SUSPENSION SYSTEM (w/ AVS): DESCRIPTION (2008 Sequoia)

DTC

C1746

Gate Solenoid Valve Circuit Malfunction

DESCRIPTION

The suspension control ECU opens the gate solenoid valve (No. 2 height control valve) to lead the compressed air to the height control cylinder (pneumatic cylinder) and to raise the vehicle height.

Further, the gate solenoid valve (No. 2 height control valve) opens and closes the passage between the right and left height control cylinders (pneumatic cylinders).

The No. 2 height control valve consists of a leveling solenoid valve and a gate solenoid valve.

The gate solenoid valve opens and closes the passage between the compressor and the height control cylinder (pneumatic cylinder).

DTC Code

Detection Condition

Trouble Area

C1746

When either of the following is detected:

  • With the height control valve inactivated, an open signal of the height control valve is detected for 1 second or more.
  • With the height control valve activated, a short signal of the valve is detected 8 times successively.
  • Wire harness or connector
  • Gate solenoid valve (No. 2 height control valve)
  • Suspension control ECU

HINT:

  • Once the ECU stores DTC C1746 in the memory, the vehicle height control is suspended until a normal signal is input to the ECU from the height control solenoid valves. However, control is resumed if the ignition switch is turned off, then to ON again.
  • Malfunction in the gate solenoid valve:

    The height control operation is suspended, and the height control indicator light does not change by operating the height control switch.

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (REAR GATE SOLENOID)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON, and turn the Techstream main switch on.

(c) Enter the following menus: Chassis / Air suspension / Active Test.

Air Suspension

Tester Display

Test Part

Control Range

Diagnostic Note

Rear Gate Solenoid

Gate solenoid valve/

ON or OFF

Operation sound of solenoid (clicking sound) can be heard

OK:

Operation of solenoid (clicking sound) can be heard

Result

Result

Proceed to

NG

A

OK (When troubleshooting according to the Problem Symptoms Table)

B

OK (When troubleshooting according to the DTC Chart)

C
A

2.

INSPECT NO. 2 HEIGHT CONTROL VALVE SUB-ASSEMBLY (GATE SOLENOID VALVE)

(a) Turn the ignition switch off.

(b) Disconnect Q4 solenoid valve connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 (LH+) - 2 (E)

20°C (68°F)

17.5 to 21.5 Ω

(d) Connect the battery positive (+) lead to terminal 1 and the negative (-) lead to terminal 2 of the solenoid valve connector. Then check that the valve makes an operating sound.

OK:

Operation of solenoid (clicking sound) can be heard

OK

3.

CHECK HARNESS AND CONNECTOR (GATE SOLENOID VALVE - ECU AND BODY GROUND)

(a) Disconnect the O16 ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Q4-1 (LH+) - O16-7 (SLRL)

Always

Below 1 Ω

Q4-1 (LH+) or O16-7 (SLRL) - Body ground

Always

10 kΩ or higher

Q4-2 (E) - Body ground

Always

Below 1 Ω
OK