DTC C1751: Compressor Relay Coil Malfunction [08/2019 - 08/2021]: Procedure

1. Turn the engine switch off.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG).
4. Turn the Techstream on.
5. 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	The operating sound of the motor can be heard. 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

Result: 

B 

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [08/2015 - ] 

Result: 

C 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - 08/2020]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2020 - 08/2021] 

Result: 

A 

See step  2

1. Turn the engine switch off.
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
   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

   Result

   Result
   OK
   NG

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *1	AIR SUS Relay

Result: 

NG 

REPLACE SUSPENSION CONTROL RELAY (AIR SUS) 

Result: 

OK 

See step  3

1. Disconnect the R22 suspension control 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
   R22-22 (RC) - Engine room relay block AIR SUS relay terminal 1	Always	Below 1 Ω
   R22-22 (RC) - Body ground	Always	10 kΩ or higher
   Engine room relay block AIR SUS relay terminal 2 - Body ground	Always	Below 1 Ω

   Result

   Result
   OK
   NG

Result: 

OK 

REPLACE SUSPENSION CONTROL ECU. Refer to  REMOVAL [08/2015 - ] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR