DTC C1751: Compressor Relay Coil Malfunction (TO 08/2009): Procedure

1. Turn the engine switch off.
2. Remove the AIR SUS relay from the engine room J/B.
   Fig 1: Identifying Suspension Control Relay Circuit Diagram

   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 battery voltage is not applied between terminals 1 and 2	10 kΩ or higher
   	When battery voltage is applied between terminals 1 and 2	Below 1 Ω

NG → REPLACE AIR SUS RELAY 

OK: Go to next step 

1. Disconnect the A54 ECU connector.
2. Remove the AIR SUS relay from the engine room J/B.
   Fig 2: Identifying A54 ECU Connector

   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
   A54-22 (RC) - J/B AIR SUS relay terminal 1	Always	Below 1 Ω
   A54-22 (RC) - Body ground	Always	10 kΩ or higher
   J/B AIR SUS relay terminal 2- Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1

   Component without relay (Engine Room J/B)

   *2

   Rear view of wire harness connector (to Suspension Control ECU)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   3