Cruise Control Operation (Description and operation) (page 4 of 4)

Other Body Control Unit (BCU) inputs/outputs

’Brakelight’ 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 BCU. The BCU sends a ’brakelight’ signal output from pin C0661-16 on a GS wire, to pin C0239-5 on the cruise control ECU.

The logic circuits in the cruise control ECU use this ’brakelight’ signal to lock out the cruise control. The internal logic of the ECU uses the ’brakelight’ 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 ’brakelight’ 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 on a K wire from cruise control ECU pin C0239-16, through header C0286, to the diagnostic socket. The information can be retrieved using TestBook/T4 or other suitable scantool.