C1751

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1751/51: Compressor Relay Coil Malfunction
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.





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 engine switch is turned off and then on (IG) again.

WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
When replacing the suspension control ECU, perform registration Testing and Inspection.

HINT
If DTC C1782/82 is output at the same time as C1751/51, perform the inspection necessary for DTC C1782/82 first C1782.

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (COMPRESSOR MOTOR RELAY)

(a) Turn the engine switch off.

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Chassis / Air suspension / Active Test.

Air Suspension





OK:

Operation of motor can be heard.

Result





C -- USE SIMULATION METHOD TO CHECK How To Proceed With Troubleshooting

B -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Air Suspension System
A -- Continue to next step.

2. INSPECT SUSPENSION CONTROL RELAY (AIR SUS)

(a) Turn the engine switch off.

(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:





Text in Illustration





NG -- REPLACE SUSPENSION CONTROL RELAY (AIR SUS)
OK -- Continue to next step.

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

(a) Disconnect the R22 suspension control 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:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE SUSPENSION CONTROL ECU Removal