DTC P1546: A/C Clutch Relay Control Circuit: Description

Ignition voltage is supplied directly to the A/C compressor clutch relay. The Powertrain Control Module (PCM) controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be about zero volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be about battery voltage. If the fault detection circuit senses a voltage other than what is expected, Diagnostic Trouble Code (DTC) P1546 will set.