Dtc C1751/51 Compressor Relay Coil Malfunction


DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (COMPRESSOR MOTOR RELAY)

INSPECT SUSPENSION CONTROL RELAY (AIR SUS)

CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - AIR SUS RELAY)

DTC C1751/51 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 the relay on.
As a result, the current flows to the AIR SUS relay coil, closing the relay contact, and then battery positive voltage is applied to the height control compressor, which causes compressed air to raise the vehicle height.

DTC Code
DTC Detection Condition
Trouble Area
C1751/51
Either condition is met:
  1. With the AIR SUS relay inactivated, an open signal of the AIR SUS relay is detected for 1 second or more.
  2. With the AIR SUS relay activated, a short signal of the AIR SUS relay is detected 8 times successively.
  1. Harness or connector
  2. AIR SUS relay (Suspension control relay)
  3. Suspension control ECU
HINT:
Once the suspension control ECU stores DTC C1751/51 in memory, vehicle height control is suspended until a normal signal is input to the suspension control ECU from the AIR SUS relay. However, control is resumed if the ignition switch is turned off and then to ON again.

WIRING DIAGRAM

except 1GD-FTV with Urea SCR System:

Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.Suspension Control.Air Suspension System. Dtc C1751/51 Compressor Relay Coil Malfunction

for 1GD-FTV with Urea SCR System:

Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.Suspension Control.Air Suspension System. Dtc C1751/51 Compressor Relay Coil Malfunction


INSPECTION PROCEDURE

NOTICE:
When replacing the suspension control ECU, perform registration (LandCruiser RM000003X4500TX.html).
HINT:
If DTC C1782/82 is output at the same time as C1751/51, perform the inspection necessary for DTC C1782/82 first (LandCruiser RM000001N9301JX.html).
1.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (COMPRESSOR MOTOR RELAY)

  1. Turn the ignition switch off.

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. 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
    1. The operating sound of the motor can be heard.
    2. When the Active Test is performed, Motor Relay in the Data List changes between ON and OFF accordingly.
    OK:
    Operation of motor can be heard.
    Result
    Result
    		Proceed to
    NG
    		A
    OK (When troubleshooting according to problem symptoms table)
    		B
    OK (When troubleshooting according to DTC chart)
    		C


B
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (LandCruiser RM000001SGQ021X.html)

C
USE SIMULATION METHOD TO CHECK (LandCruiser RM000003YMJ00XX.html)
A


2.INSPECT SUSPENSION CONTROL RELAY (AIR SUS)

  1. Turn the ignition switch off.

  1. Remove the AIR SUS relay from the engine room relay block.



    Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.Suspension Control.Air Suspension System. Dtc C1751/51 Compressor Relay Coil Malfunction

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

    Standard Resistance:
    Tester Connection
    		 Condition
    		Specified Condition
    3 - 5
    		12 V battery voltage is not applied to terminal 1 and 2
    		10 kΩ or higher
    12 V battery voltage is applied to terminal 1 and 2
    		Below 1 Ω
    Text in Illustration
    *1
    		AIR SUS Relay


NG
REPLACE SUSPENSION CONTROL RELAY (AIR SUS)
OK


3.CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - AIR SUS RELAY)

  1. Disconnect the R19 suspension control ECU connector.

  1. Remove the AIR SUS relay from the engine room relay block.

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

    Standard Resistance:
    except 1GD-FTV with Urea SCR System:
    Tester Connection
    		 Condition
    		Specified Condition
    R19-22 (RC) - Engine room relay block AIR SUS relay terminal 1
    		Always
    		Below 1 Ω
    R19-22 (RC) - Body ground
    		Always
    		 10 kΩ or higher
    Engine room relay block AIR SUS relay terminal 2 - Body ground
    		Always
    		Below 1 Ω
    for 1GD-FTV with Urea SCR System:
    Tester Connection
    		 Condition
    		Specified Condition
    R19-22 (RC) - Engine room relay block AIR SUS relay terminal 2
    		Always
    		Below 1 Ω
    R19-22 (RC) - Body ground
    		Always
    		 10 kΩ or higher
    Engine room relay block AIR SUS relay terminal 1 - Body ground
    		Always
    		Below 1 Ω


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE SUSPENSION CONTROL ECU (LandCruiser RM000002BGR01UX.html)