Gear position indicator illumination (Body control unit)

Odometer update The BCU can be programmed for one of two options: l Option 1 – no odometer error warning. l Option 2 – odometer error warning.

In order to provide an LCD flash request to the instrument pack via the communications link, the following inputs are checked: l Ignition state. l Instrument pack odometer value (via the communications link). l BCU odometer value.

The function is only active when the ignition state is on. The maximum allowed value is 999,999 miles (1,608,999 km).If the instrument pack odometer value is greater than the maximum allowed value, the maximum value is assumed. The BCU odometer value is stored in EEPROM. If 16 identical values of the instrument pack odometer reading is received consecutively, the instrument pack odometer value is compared with the BCU odometer value. If the consecutive readings from the instrument pack differ, the BCU odometer value is incremented accordingly. If the BCU odometer value is less than the instrument pack odometer value by up to 10 km, the BCU odometer value is set equal to the instrument pack odometer value.

If the odometer warning option is enabled, and the contents of the instrument pack odometer value buffer is identical to, or greater than BCU odometer value ± 10 km, the BCU sends an LED flash request to the instrument pack.

In the event of a communications link failure, this function will be unable to operate.

Gear position indicator illumination

On automatic gearbox models, two variations of illumination for the gear position indicators on the selector lever can be programmed into the BCU. In option 1, illumination is provided when the ignition is on. In option 2, illumination is enabled when the ignition is on and the side lamps are off.

Starter relay

The BCU checks the status of the following inputs and internal BCU conditions to determine whether or not to provide an output to enable the starter relay: l Autostart inhibit (vehicles with automatic gearbox only). l Security start inhibit (immobilisation check). l Engine running (link to instrument pack). l EEPROM locked (internal check). l IDM and BCU matched.

When the BCU receives a crank signal from the ignition switch, an earth path is completed to the starter relay coil, provided that the security system has been de-activated. If the ECM has not received a valid unlock/ remobilise signal, the starter relay will be disengaged and the engine stopped. The BCU also receives an engine running signal from the instrument pack, so that if the ignition key is turned to the crank position while the engine is running, the starter motor relay will not be engaged.

If the logic conditions are correct to allow starter operation, the completion of the earth path from the starter relay coil to the BCU energises the coil and the relay contacts close to supply battery power to the starter motor.

When the ignition switch is released from the crank position, the power supply feed from the ignition switch to the starter relay coil is interrupted and the relay contacts open to prevent further battery feed to the starter motor.

If a communications link failure is experienced, the BCU will be prevented from detecting the 'engine running' condition and the BCU will default to assume that the engine is not running.