Circuit Description
WARNING: This page is about a different car, the 2002 Cadillac Eldorado and 2001 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
With the ignition ON, ignition 1 voltage is supplied to the coil side feed of the PARK relay. The control circuit of the PARK relay is controlled by the PZM. When the PZM receives a class 2 serial data message from the PCM stating that the automatic transmission is in the PARK position, the PZM grounds the control circuit of the PARK relay via an internal switch called a driver. The driver supplies a path to ground for the component being controlled. Each driver has a fault line which the PZM monitors. When the PZM commands the PARK relay ON, the voltage of the control circuit should be low, near 0 volts. If the circuit voltage is measured above the fault line, the DTC is set.