Last Modified: 11-29-2007 1.6 C
Service Category: Suspension Section: Suspension Control System
Model Year: 2008 Model: Sequoia Doc ID: RM000001N9F008X
Title: SUSPENSION CONTROL: AIR SUSPENSION SYSTEM (w/o AVS): DESCRIPTION (2008 Sequoia)

DTC

C1751

Compressor Relay Coil Malfunction

DESCRIPTION

When the "UP" side of the height control switch is pressed, a signal is sent from terminal RC of the suspension control ECU to the AIR SUS relay to turn it on.

As a result, the current flows to the AIR SUS relay coil, closing the relay contact, and then the battery positive voltage is applied to the compressor, which causes the compressed air to raise the vehicle height.

DTC Code

Detection Condition

Trouble Area

C1751

When either of the following is detected:

  • With the AIR SUS relay inactivated, an open signal of the AIR SUS relay is detected for 1 second or more.
  • With the AIR SUS relay activated, a short signal of the AIR SUS relay is detected 8 times successively.
  • Wire harness or connector
  • AIR SUS relay
  • Suspension control ECU

HINT:

Once the ECU stores DTC C1751 in the memory, the vehicle height control is suspended until a normal signal is input to the ECU from the AIR SUS relay. However, control is resumed if the ignition switch is turned off, then to ON again.

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (COMPRESSOR MOTOR RELAY)

(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

Compressor Motor Relay

AIR SUS relay

ON or OFF

Operation 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 SUSPENSION CONTROL RELAY (AIR SUS)

(a) Turn the ignition switch off.

(b) Remove the AIR SUS relay from the engine relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

When 12 V battery voltage is not applied to terminal 1 and 2

10 kΩ or higher

When 12 V battery voltage is applied to terminal 1 and 2

Below 1 Ω
OK

3.

CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL RELAY - ECU AND BODY GROUND)


(a) Disconnect the O19 ECU connector.

(b) Remove the AIR SUS relay from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

O19-5 (RC) - Relay block AIR SUS relay terminal 1

Always

Below 1 Ω

O19-5 (RC) or Relay block AIR SUS relay terminal 1 - Body ground

Always

10 kΩ or higher

Relay block AIR SUS relay terminal 2 - Body ground

Always

Below 1 Ω
OK