Freelander System Description and Operation
ENGINE MANAGEMENT SYSTEM - SIEMENS
18-4-46 DESCRIPTION AND OPERATION
Cruise Control Description
General
The cruise control system is integrated with the engine management system and uses throttle intervention to
automatically maintain a set vehicle speed. Once engaged, the system can also be used to accelerate the vehicle
without using the accelerator pedal. The cruise control system consists of:
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A master switch.
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SET+ and RES steering wheel switches.
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An interface ECU.
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A warning lamp.
The system also uses:
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Inputs from the brake pedal sensor and the Anti-lock Braking System (ABS) modulator.
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The Engine Control Module (ECM).
The Controller Area Network (CAN) bus is used by the cruise control system for the exchange of data between the
interface ECU, ECM, EAT ECU, ABS modulator and instrument pack.
Cruise control is enabled when the master switch is pressed. Once enabled, the cruise control system is operated
using the steering wheel switches. The steering wheel switches output signals to the interface ECU, which then
signals the ECM. The ECM then adjusts the throttle to maintain the vehicle at the set speed.
The cruise control warning lamp provides a visual indication of when the system is engaged.
Master Switch
The master switch controls an ignition feed to the interface ECU to enable the system. The switch is a mechanically
latching push switch installed on the outboard side of the instrument pack. An amber LED in the switch remains
illuminated while the switch is latched.
Steering Wheel Switches
The steering wheel switches, SET+ and RES, are non latching push switches that engage and disengage cruise
control and adjust the set speed. While pressed, the switches connect a power feed from the battery, via the coil of
the horn relay and the rotary coupler, to the interface ECU.
Interface ECU
The interface ECU converts the analogue signals from the steering wheel switches into serial data messages, known
as Multi-Function Logic (MFL) messages, which are interpreted by the ECM to operate cruise control. The interface
ECU also controls the output of a cruise engaged signal to the EAT ECU. The interface ECU is installed below the
RH front seat, under a plastic protective cover.