Cruise Control Operation (Description and operation) (page 3 of 4)

Cruise resume/suspend When the res/suspend switch is operated, the switch contacts close and connect the feed from the horn relay to cruise control ECU pin C0239-2, via the rotary coupler and a UW wire. If cruise control is engaged, this signal suspends cruise control operation. If cruise control is suspended, the signal will initiate the cruise control ECU to engage cruise control at the speed retained in the ECU’s memory.

Cruise control pump The cruise control pump has three connections to the cruise control ECU. One connection on a WU wire from pin C0239-11 supplies power directly to the pump. The control valve solenoid and dump valve solenoid are connected to pin C0239-17 of the cruise control ECU on a BY wire. The pump is earthed via pin C0239-7 of the cruise control ECU on a BR wire.

The dump valve solenoid is connected via header C0287 LHD/C0290 RHD on a GP wire to the contacts of the brake pedal switch. In normal operation the coil of the dump valve is earthed by the brake light circuit, via the contacts of the the brake pedal switch. When the brake pedal is pressed power is supplied on the earth path of the dump valve solenoid. When the voltage on each side of the coil of the dump valve solenoid is equalised, there is no voltage drop across the solenoid. With no current flowing through the coil of the dump valve solenoid, the solenoid is de-energised and the dump valve opens.

When the cruise control switch is on and vehicle speed is more than 28 mph (45km/h) and less than 125 mph (201 km/h), the cruise control ECU supplies power to the pump and valve solenoids. The earth paths for the pump and the control valve solenoid are switched as required by the cruise control ECU to set and maintain vehicle speed.