CRUISE CONTROL
B5
CIRCUIT OPERATION
REV: 08/99
2
System Disable
The cruise control system can be disabled in one of
four ways:
1. The Cruise Control Switch (X115) is put in the 0
position, removing the BeCM (Z238) power from
the Cruise Control ECU (Z121) and vacuum
pump, and erasing the set speed memory.
2. The RES/DECEL Switch is depressed, signalling
the Cruise Control ECU (Z121) via the Inverter/
Converter (Z249) to disengage the system.
3. The brake pedal is depressed and a vacuum val-
ve in the Switch Vent Valve opens (X112). This
vents vacuum to the actuator valve and releases
the throttle.
4. The Voltage applied to the Cruise Control ECU
(Z121) terminal 1 is interrupted, causing the
Cruise Control ECU (Z121) to turn off the
vacuum pump and de–energize the vacuum
solenoid valve. This voltage path is interrupted
when:
D
The brake pedal is depressed. With the brake
pedal depressed, the Brake Switch Vent Valve
(X112) moves to position 1 and the circuit is in-
terrupted.
D
The transfer gear box is not in Hi range.
D
The vehicle speed does not exceed 28 mph (45
km/h).
D
The vehicle is not in a forward gear (P, R, or N)
(Automatic Transmission).
D
The clutch pedal is depressed (Manual
Transmission).
D
The engine rpm rises above 5000
±
10%
(Manual Transmission).
The BeCM (Z238), which monitors these signals, will
then remove power from C1279/Pin 18.
Diesel Engine
For vehicles equipped with a manual transmission,
cruise control can only be activated when the Cruise
Control Switch (X115) is depressed and the clutch
pedal is not depressed. The Diesel Engine Control
Module (Z132) will not allow the engine to overspeed
if a cruise control speed is requested that is beyond
the capability of the engines speed range.
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 C1279/Pin 14 of the BeCM
(Z238). The X, Y, and Z switch status (PRND321
position information) from the gearbox position
switch is applied to C1287/Pins 8, 9, and 18 of the
BeCM (Z238). The clutch pedal position input is
applied to C1279/Pin 4 and the engine speed input is
applied to C1288/Pin 9 of the BeCM (Z238). The
BeCM (Z238) then supplies voltage, via its Pin 18 to
the Inverter/Converter (Z249) and to the “Operation”
bulb of the Cruise Control Switch (X115).
The Cruise Control Converter/Inverter Module
(Z249) supplies the Engine Control Module (Z132)
via its pin 4 with a voltage signal to “switch on” the
cruise circuit. For the Diesel Engine, the Engine
Control Module (Z132) controls the cruise circuit as
the Cruise Control ECU (Z121) does for the Petrol
Engine. The Engine Control Module (Z132) is also
responsible for the acceleration/deceleration of the
vehicle.