Wagoneer L6-242 4.0L VIN L FI (1989)
Fig. 27 - Relay Circuitry
SYSTEM RELAYS
Three relays used in the anti-lock system are:
^
Modulator Power Relay
^
Yellow Light Relay
^
Booster Pump Motor Relay
The modulator power and yellow light relays are both resistor suppressed and are both located under the hood on the left inner fender panel (fig.
25). The booster pump motor relay is diode suppressed and is located next to the booster pump and motor assembly (fig. 26).
When the system is powered up (2 seconds after engine start-up), the ECU supplies power (12 Volts) to the modulator solenoids through the
modulator power relay (fig. 27). When the modulator power relay closes, battery power is sent to the yellow light relay which opens and turns the
yellow light off during normal operation.
The booster pump relay is not controlled by the ECU. It is controlled by a pressure switch located in the pump assembly. When energized by the
pressure switch, the relay closes, energizing the booster pump motor.
