Engine management system - EDC (Description): Description and operation

Description

General

The cruise control system is integrated with the engine management system and uses fuelling 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: l A master switch. l SET+ and RES steering wheel switches. l An interface ECU. l A warning lamp.

The system also uses: l Inputs from the brake pedal position sensor and the Anti-lock Braking System (ABS) modulator. BRAKES, DESCRIPTION AND OPERATION, Description. l The Engine Control Module (ECM). ENGINE MANAGEMENT SYSTEM - EDC, DESCRIPTION AND OPERATION, Description.

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. In the cruise control mode, the ECM adjusts the pulse width of the fuel injector signals to adjust the fuel supply as necessary 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 in the centre console switch panel. A green 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.

MFL Messages The ignition power supply from the master switch activates the interface ECU, which then monitors the inputs from the steering wheel switches and the cruise control status message from the CAN bus. From these, the interface ECU determines when to output one of three MFL messages, RESUME, SET or OFF, on the serial link to the ECM. Each time the interface ECU is enabled by the power feed from the master switch, the output of the RESUME message is automatically inhibited until after the first engagement of cruise control.

Cruise Engaged Signal When cruise control is engaged, the interface ECU outputs battery voltage on a connection to the EAT ECU to provide a cruise control engaged signal. The EAT ECU uses the signal to switch between normal and cruise control modes of operation.