Operation
When the cruise control switch is on, the feed from fuse 30 in the passenger compartment fusebox, passes through the cruise control switch contacts to provide power input to the cruise control ECU pin C0239-8 on a WY wire.
Simultaneously, the feed also passes through the cruise control switch indicator lamp which illuminates. The indicator lamp is connected to earth on a black wire via header C0760 to earth header C0017 LHD/C0018 RHD. The cruise control ECU is earthed on a B wire from pin C0239-18, via header C0286 LHD/C0291 RHD to earth header C0018 LHD/C0017 RHD.
When the brake or clutch pedal or is not depressed, the feed from fuse 25 in the passenger compartment fusebox flows to a pair of contacts in the brake pedal switch on a GO wire. A connection from header C0287 LHD/C0290 RHD is connected to the coil of the dump valve in the cruise control pump. In normal operation the coil is earthed by the brake light circuit, via the contacts of the brake pedal switch.
Manual transmission
The feed passes from the contacts of the brake pedal switch and is connected to the clutch pedal switch by an OG wire. The feed passes through the closed contacts of the clutch pedal switch to a PG wire that is connected to pin C0239-1 on the cruise control ECU. This feed provides the power source to the cruise control pump via the cruise control ECU.
If either the clutch pedal or the brake pedal is depressed, the respective switch contacts will be opened, removing power from the cruise control ECU and disengaging cruise control. If the cruise control switch remains on, the previous speed will be retained in the cruise control ECU memory.
The previous speed can be resumed by operation of the resume/suspend switch. The cruise control ECU will engage the cruise control if:
- The vehicle is travelling at over 28 mph (45 km/h)
- The cruise control switch is still on and has not been turned off
- The brake pedal is not depressed.
- The clutch pedal is not depressed.
Automatic transmission (NAS)
The feed from the contacts of the brake pedal switch is connected on a PG wire to pin C0239-1 on the cruise control ECU. The feed from the brake pedal switch provides the power source to the cruise control pump via the cruise control ECU.
The cruise control ECU will engage the cruise control if:
- The vehicle is travelling at over 28 mph (45 km/h)
- The gearbox selector position is acceptable to the cruise control ECU
- The cruise control switch is still on and has not been turned off The brake pedal is not depressed.
Automatic transmission (ROW)
The feed from the contacts of the brake pedal switch is connected by a PG wire to pin C0239-1 on the cruise control ECU. The feed from the brake pedal switch provides the power source to the cruise control pump via the cruise control ECU.
NOTE: On vehicles with premium ICE systems, the feed from the contacts of the brake pedal switch is connected by an OG wire to connector interface C0712-2/C0667-1. From the connector interface the feed continues on a PG wire to the cruise control ECU.
The cruise control ECU will engage the cruise control if:
- The vehicle is travelling at over 28 mph (45 km/h)
- The gearbox selector position is acceptable to the cruise control ECU
- The cruise control switch is still on and has not been turned off
- The brake pedal is not depressed.
Speed signal
The cruise control ECU receives a speed signal input on a KG wire via header
C0290 to pin C0239-15, from pin C0504-3 on the SLABS ECU.
Cruise set/accelerate
When the set/accel switch is operated, a feed is supplied from the BCU pin C0664-4 on a P0 wire, through header C0291 LHD/CO286 RHD and the rotary coupler, to the set/accel switch.
When the set/accel switch contacts are closed, the feed continues on an RW wire through the rotary coupler, to the cruise control ECU pin C0239-4. This signal initiates the cruise control ECU to activate the cruise control pump functions, providing all other parameters are correct.
Cruise resume/suspend
When the res/suspend switch is operated, a feed is supplied on a P0 wire from the BCU pin C0662-4, through header C0291 LHD/CO286 RHD and the rotary coupler, to the res/suspend switch.
With the res/suspend switch contacts closed, the feed continues from the res/suspend switch, through the rotary coupler, and on a UW wire to the cruise control ECU pin C0239-2 on a UW wire. If cruise control is engaged, this signal suspends cruise control operation. If cruise control is suspended, the signal will initiate the cruise control ECU to engage cruise control at the speed retained in the ECU's memory.
Cruise control pump
The cruise control pump has three connections to the cruise control ECU. One connection on a WU wire from pin C0239-11 supplies power directly to the pump.
The control valve solenoid and dump valve solenoid are connected to pin CO239-17 of the cruise control ECU on a BY wire. The pump is earthed via pin C0239-7 of the cruise control ECU.
The dump valve solenoid is connected via header C0287 LHD/C0291 RHD on a OP wire to the contacts of the brake pedal switch. In normal operation the coil of the dump valve is earthed by the brake light circuit, via the contacts of the the brake pedal switch. When the brake pedal is pressed power is supplied on the earth path of the dump valve solenoid. When the voltage on each side of the coil of the dump valve solenoid is equalized, there is no voltage drop across the solenoid. With no current flowing through the coil of the dump valve solenoid, the solenoid is de-energized and the dump valve opens.
When the cruise control switch is on and vehicle speed is more than 28 mph (45 km/h) and less than 125 mph (201 km/h), the cruise control ECU supplies power to the pump and valve solenoids. The earth paths for the pump and the control valve solenoid are switched as required by the cruise control ECU to set and maintain vehicle speed.
Other Body Control Unit (BCU) inputs/outputs
'Brake Light' Signal
If the brake pedal is depressed a pair of contacts in the brake pedal switch allow a feed to flow on a GP wire via header C0287 LHD/C0290 RHD to pin C0661-7 on the BGU. The BCU sends a 'brake light' signal output from pin C0661-16 on a GS wire, to pin C0239-18 on the cruise control ECU.
The logic circuits in the cruise control ECU use this 'brake light' signal to lock out the cruise control. The internal logic of the ECU uses the 'brake light' signal to cancel cruise control by interrupting the earth path to the pump, and activating the dump valve solenoid. The dump valve opens the vacuum chamber to ambient air pressure, the vacuum is dissipated and the throttle actuator no longer has an effect on the throttle position.
Gearbox inputs - automatic transmission
An Input for Park, Neutral and Reverse positions are passed from the gearbox position selector on a BG wire via splice joint A31 and connectors C0668-5, C0681-5 to pin C0663-11 of the BCU.
If an input from the gearbox position selector or the brake pedal switch is received by the BCU, a 'brake light' signal is sent from the BCU to the cruise control ECU, This signal will cancel or inhibit cruise control operation.
Gearbox inputs - manual transmission
There are no signals from the manual gearbox to the BCU. The BCU is permanently connected to earth header C0552 via a BG wire from pin C0663-11 through connectors C0668-5 and C0661-5 to splice joint A33. From splice joint A33 the earth continues on a B wire through connectors C0681-8 and C0668-8 to earth header C0552.
Diagnostic socket - all models
Diagnostic information can be retrieved or a K wire from cruise control ECU pin
C0239-16, through header C0286, to the diagnostic socket. The information can be retrieved using TestBook or other suitable scantool.