Cruise control – circuit operation

CRUISE CONTROL – CIRCUIT OPERATION

CIRCUIT OPERATION

Petrol Engine

For vehicles equipped with a manual transmission, cruise control can only be activated when the Cruise Control Switch (X115) is depressed, the transfer gear box is in Hi range, and the clutch pedal is not depressed. Also, the BeCM (Z238) will deactivate cruise control if the engine rpm rises above 5000 ± 10%, due to the possibility of selecting gears manually without the use of the clutch. For vehicles equipped with an automatic transmission, cruise control can only be activated when the Cruise Control Switch (X115) is depressed, the transfer gear box is in Hi range, and the transmission is in one of the forward gears. With the Cruise Control Switch (X115) on, a ground signal is applied to C255/Pin 14 of the BeCM (Z238).The BeCM (Z238) then suplies signal voltage via its Pin 18 to the Converter/Inverter (Z249), to Pin 10 of the Cruise Control ECU (Z121) and to the “Operation” bulb of the Cruise Control Switch (X115). The transfer gearbox Hi range status from the Transfer Gear Box ECU (Z256) is applied to C626/Pin 3 of the BeCM (Z238). The X, Y, and Z switch status (PRND321 position information) from the gearbox position switch is applied to C626/Pins 8, 9, and 18 of the BeCM (Z238). The clutch pedal position input is applied to C255/Pin 4 and the engine speed input C112/Pin 9 of the BeCM (Z238). When the transfer gearbox is in Hi range, a forward gear is selected and the Cruise Control Switch (X115) is on, theBeCM (Z238) suplies voltage via C258/Pin 1 and the Brake Switch Vent Valve (X112) to the Cruise Control ECU (Z121) Pin 9, which then “knows” that cruise control can be operated. When cruise control is activated and a cruise speed is set, the Cruise Control ECU (Z121) applies voltage through the OU wire and ground through the OR wire to operate the Cruise Control Vacuum Pump (M103) motor. The Cruise Control ECU (Z121) applies ground through the OK wire to close the normally open solenoid valve in the pump. The pump applies vacuum to the actuator.

SET/ACCEL

To set a cruise speed, the Cruise Control Switch (X115) must be on and vehicle speed must exceed 28 mph (45 km/h). When the SET/ACCEL Switch is depressed under these conditions, the Converter/Inverter (Z249) is supplied with a ground

signal. This signal is “converted” to a voltage signal and is transmitted via the SY wire to the Cruise Control ECU (Z121) terminal 3, causing the vacuum pump to operate. When the SET/ACCEL Switch is released, the signal is removed from terminal 3, signalling the ECU to set the speed.

RES/DECEL

When the RES/DECEL Switch is depressed, a signal is applied via the RY wire to terminal 4 of the Cruise Control ECU (Z121). This tells the ECU (Z121) to disengage the system and the vehicle slows down. When the switch is depressed a second time, the signal is again applied to the ECU (Z121) and the vehicle returns to the previously set speed.

Speed Input

Terminal 11 of the Cruise Control ECU (Z121) receives the Vehicle Speed output signal from the BeCM (Z238) through the Y or YR wire. The BeCM (Z238) receives the vehicle speed signal from the Anti-lock Brake System ECU (Z108). The signal is a pulsing voltage and its frequency changes with vehicle speed.