Cruise Control Operation

OPERATION

General
Feed from the positive battery terminal (C0192) is supplied to the main relay, the horn relay, and fusible link 3 (C0632) on an R wire. All are located in the engine compartment fuse box.

The earth path for the main relay (C0576) is controlled by the ECM (C0604) on an NG wire. The energized main relay provides a feed to fuse 4, which is also located in the engine compartment fuse box.

Fusible link 3 (C0571) is connected to the ignition switch (C0028) by an N wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C0028) to fuse 35 of the passenger compartment fuse box (C0588) on a G wire.

Cruise Control Master Switch
Cruise control is switched on and off by pressing the master switch mounted on the center console. Fuse 35 of the passenger compartment fuse box (C0580) supplies the cruise control master switch (C0749) an ignition feed on a W wire. When the switch is pressed, current flows across the switch contacts (C0749) to the cruise control interface unit (C1959) on a WY wire.


NOTE: When the cruise control system is switched off using the master switch, any stored road speed values will be lost.


Cruise Control Interface Unit
Fuse 4 of the engine compartment fuse box (C0575) provides a feed to the cruise control interface unit (C1959) on an NK wire. The interface unit (C1959) is earthed on a B wire. To enable it to control the cruise control system, the ECU receives a number of inputs from various sources as follows:

ABS ECU
The ABS ECU (C0501) provides a road speed signal to the cruise control interface unit (C1959) via the CAN-BUS on YN (Low) and YB (High) wires.

Set + Switch
A constant battery feed is supplied to the rotary coupler (C0082) via the horn relay (C0576) on a PY wire. Current flows across the rotary coupler (C1254) to the cruise control switches. The 'Set +' switch is a normally open, non-latching switch. When the switch is pulled forward, the switch contacts close. Current flows across the switch back to the rotary coupler. The rotary coupler (C0082) is connected to the cruise control interface unit (C1959) by an RW wire.

The interface unit (C1959) converts the signals received from the 'Set +' switch, and relays information to the Engine Control Module (ECM) (C0331) on an RG wire. The signal provided by the interface unit is a continuous, pulsed voltage, varying from approximately 6 V to 8 V. By measuring the frequency of the pulses, the ECM is able to control vehicle speed in accordance to requests from the 'Set +' switch.

Res switch
A constant battery feed is supplied to the rotary coupler (C0082) via the horn relay (C0576) on a PY wire. Current flows across the rotary coupler (C1254) to the cruise control switches. The 'Res' switch is a normally open, non-latching switch. When the switch is pulled forward, the switch contacts close. Current flows across the switch back to the rotary coupler. The rotary coupler (C0082) is connected to the cruise control interface unit (C1959) by a UW wire.

The interface unit (C1959) converts the signals received from the 'Res' switch, and relays information to the ECM (C0331) on an RG wire. The signal provided by the interface unit is a continuous, pulsed voltage, varying from approximately 6 V to 8 V. By measuring the frequency of the pulses, the ECM is able to control vehicle speed in accordance to requests from the 'Res' switch.

Brake Pedal Switch
Fuse 35 of the passenger compartment fuse box (C0580) provides an ignition feed to the hall effect brake pedal switch (C0652) on a W wire. The brake pedal switch (C0652) is earthed on a B wire.

When the brake pedal is in the rest position, only a nominal voltage (between approximately 0 V and 2 V) is supplied to the ECM (C0331) on GR and PG wires. When the brake pedal is pressed, this voltage rises to between approximately 6 V and battery voltage. Sensing this increase, the ECM suspends cruise control operation.

Electronic Automatic Transmission (EAT) ECU
When cruise control is active, the cruise control interface unit (C1959) provides a feed to the EAT ECU (C0932) on a WU wire. When the EAT ECU receives this feed, it enters its cruise control mode.

Instrument Pack
When cruise control is operational, the cruise control interface unit (C1959) sends a 'cruise active' message to the instrument pack (C0230) via the CAN-BUS on YN (low) and YB (high) wires. This message is used to illuminate the cruise control lamp housed within the instrument pack.