Engine management system - siemens (all except NAS) (Description): Description and operation

Description

General

The cruise control system is an electro-pneumatic system that 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: l A master switch. l SET+ and RES steering wheel switches. l An interface ECU. l A cruise control ECU. l A warning lamp. l A vacuum pump assembly. l A vacuum actuator.

The system also uses inputs from: l The brake pedal position sensor, brake pedal switch and Anti-lock Braking System (ABS) modulator. BRAKES, DESCRIPTION AND OPERATION, Description. l The Engine Control Module (ECM). ENGINE MANAGEMENT SYSTEM - SIEMENS (ALL EXCEPT NAS), DESCRIPTION AND OPERATION, Description.

Cruise control is enabled when the master switch is pressed and the vehicle is in a suitable driving configuration. Once enabled, the cruise control system is engaged using the steering wheel switches. The steering wheel switches output signals to the cruise control ECU, which runs the vacuum pump assembly to operate the vacuum actuator and produce the required control of the throttle.

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 and the cruise control 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 SET+ and RES steering wheel switches 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 cruise control ECU.

Interface ECU

The interface ECU controls the output of a power supply which is used by the cruise control ECU to operate the vacuum pump assembly. The interface ECU is installed below the front RH seat, adjacent to the cruise control ECU, below a plastic protective cover. The power supply is output to the cruise control ECU when the system is enabled by the master switch.

Interface ECU Harness Connector (C0895)