Circuit Operation
With the valve relay disengaged, all valve lines and the valve relay feedback line to EBCM pin 32 are held to ground by the relay. See Fig 1 . When the valve relay feedback line is held to ground, the ABS Fault line (EBCM pin 29) is also held to ground through the ABS diode. The ABS fault line is also connected to BCM pin 3D3. When the ABS fault line is held low, anti-lock function is disabled and the BCM displays the ANTI-LOCK DISABLED message on the Climate Control Driver Information Center (CCDIC).
The valve relay is engaged during normal system operation. At key-on initialization, the EBCM commands the valve relay on by grounding the valve relay actuation line (EBCM pin No. 28). When the pressure monitoring module senses that the valve relay actuation line has been grounded, the module provides a ground for the valve relay coil. With the relay engaged, battery power is provided to the valves and the valve relay feedback line (EBCM pin No. 32). The valve relay will remain engaged until the ignition is turned off, unless a failure is detected and the EBCM or pressure monitoring module command the valve relay to disengage.