Discovery 2. Manual — part 494

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-55

DESCRIPTION AND OPERATION

Cruise control component layout

1 Cruise control ECU
2 Cruise control master switch
3 SET+ switch
4 RES switch
5 Brake pedal switch
6 Clutch pedal switch

7 BCU
8 Vacuum pump assembly
9 Pneumatic actuator

10 SLABS ECU
11 Automatic gear selector lever

ENGINE MANAGEMENT SYSTEM - V8

18-2-56 DESCRIPTION AND OPERATION

Cruise control block diagram

1 SLABS ECU
2 BCU
3 Cruise control master switch
4 SET+ switch
5 RES switch
6 Brake pedal switch

7 Clutch pedal switch
8 Cruise control ECU
9 Vacuum pump assembly incorporating

pneumatic actuator

10 Automatic gear selector lever

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-57

Description - cruise control

General
All markets have a common cruise control system. The cruise control system, when activated, regulates vehicle
speed. The system consists of an electrical sub-system and a mechanical sub-system.

The electrical sub-system consists of the following components:

l

Cruise control master switch (on/off switch).

l

SET+ switch.

l

RES switch.

l

Cruise control ECU.

l

Vacuum pump assembly.

l

Brake pedal switch.

l

Clutch pedal switch (manual gearbox only).

l

SLABS ECU (speed signal).

l

BCU (brake pedal switch and automatic gearbox gear selector lever position signal).

The mechanical sub-system consists of the following components:

l

Pneumatic actuator.

l

Vacuum pump.

The cruise control ECU controls the cruise control system. It is located on the right hand A post.

The system has diagnostic capabilities through TestBook.

WARNING: To avoid the risk of losing control of the vehicle, do not use cruise control on winding, snow
covered or slippery roads, or in traffic conditions where a constant speed cannot be safely maintained. In
these conditions and at any time the system is not being used, ensure the cruise control switch is OFF.

Cruise control master switch

The cruise control master switch switches the system on and off. When the cruise control master switch is on, an
LED within the switch illuminates. If the cruise control master switch is off, cruise control will not operate. The switch
provides a 12 Volt feed to the cruise control ECU.

The cruise control master switch is located on the instrument panel near the steering column.

ENGINE MANAGEMENT SYSTEM - V8

18-2-58 DESCRIPTION AND OPERATION

Input/Output
The input from the cruise control master switch to the cruise control ECU is either a 12 Volts ignition feed or an open
circuit. 12 Volts indicates that the cruise control master switch is on and the system can be activated. An open circuit
indicates that the cruise control master switch is off and cruise control cannot be activated.

TestBook will not communicate with the cruise control ECU if the cruise control master switch is off.

SLABS ECU

The SLABS ECU provides the road speed signal to the cruise control ECU. This is the same speed signal provided
to the ECM. Cruise control will only operate between 28 - 125 mph (45 - 200 km/h). Cruise control will not operate if
a road speed signal is not present.

Input/Output

The input from the SLABS ECU to the cruise control ECU is a square wave oscillating between 0 - 12 Volts at a
frequency of 8,000 pulses per mile (1.6 km).