DTC C1751: Compressor Relay Coil Malfunction [08/2015 - 08/2019]: 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 it on.

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

DTC Code	Detection Condition	Trouble Area
C1751	When either of the following is detected: With the AIR SUS relay inactivated, an open signal of the AIR SUS relay is detected for 1 second or more. With the AIR SUS relay activated, a short signal of the AIR SUS relay is detected 8 times successively.	Wire harness or connector AIR SUS relay Suspension control ECU

HINT:

Once the ECU stores DTC C1751 in the memory, the vehicle height control is suspended until a normal signal is input to the ECU from the AIR SUS relay. However, control is resumed if the ignition switch is turned off, then to ON again.