DTC C1751: Compressor Relay Coil Malfunction [08/2015 - 08/2019]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON, and turn the Techstream main switch on.
3. 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

Result: 

B 

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE 

(Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2015 - ] )

Result: 

C 

USE SIMULATION METHOD TO CHECK 

(Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2015 - 08/2017] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2017 - 08/2018] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2018 - 08/2019] )

Result: 

A 

See step  2

1. Turn the ignition switch off.
2. Remove the AIR SUS relay from the engine relay block.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

3. 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

Result: 

NG 

REPLACE SUSPENSION CONTROL RELAY 

Result: 

OK 

See step  3

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Disconnect the O18 ECU connector.
2. Remove the AIR SUS relay from the engine room relay block.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   O18-22 (RC) - Relay block AIR SUS relay terminal 1	Always	Below 1 Ω
   O18-22 (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

Result: 

OK 

REPLACE SUSPENSION CONTROL ECU 

(Refer to REMOVAL [08/2015 - ] )

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR