CURRENT LIMITING Volvo C70 II

CURRENT LIMITING

The central electronic module (CEM) checks and sometimes limits the current from the battery and generator. The central electronic module (CEM) can prioritize between different loads in the prevailing conditions.

If there is a fault with current limitation, the general warning lamp will light in the driver information module (DIM) and a text message will be displayed.

Scheme 435

The secondary battery is used in the function automatic start/stop of engine.

The secondary battery is only connected to the vehicle's electrical system when the engine is restarted after autostop and when the secondary battery needs to be charged. Connecting the secondary battery to the vehicle's electrical system is controlled by Engine control module (ECM) via a relay.

Central electronic module (CEM) is monitors the secondary battery's voltage and controls the secondary battery's charging.

When the secondary battery needs charging the Central electronic module (CEM) sends a request to Engine control module (ECM) to connect the secondary battery to the vehicle's electrical system. When the alternator is charging and secondary battery is connected, the battery is charged.

Note. When restarting the engine, it is only Engine control module (ECM) that controls connection of the secondary battery.

When the engine is on (alternator charging) and the secondary battery is connected to the vehicle's electrical system, the secondary battery's voltage will be the same as the rest of the electrical system's voltage. If the secondary battery is disconnected, the voltage will be lower.

The secondary battery's voltage can be diagnosed.

Scheme 436

Note. From structure week 201020- the battery monitoring sensor (BMS) is LIN-connected to Central electronic module (CEM) instead of to Engine control module (ECM) as before. (For D4164T the battery monitoring sensor is still connected to Engine control module (ECM).)

The battery monitoring module is fitted on the battery's negative terminal and its main function is to monitor battery status.

Scheme 437

The headlamps are operated via the light switch module (LSM). This is on the dashboard at the side of the steering wheel. The light switch module (LSM) is directly connected to the central electronic module (CEM). Low and high beam are operated by moving the left-hand control stalk towards the steering wheel.

Low beam is powered directly by the central electronic module (CEM). High beam is powered via a directly connected relay on the central electronic module (CEM). The level of the supply voltage to the low beam is regulated by the central electronic module (CEM). When the supply voltage is sufficient (in excess of 13 V), pulse width modulation is used to maintain the voltage level at 13.0 V +/- 0.2 V. This does not apply to cars with Bi-Xenon lamps.

Cars with Bi-Xenon lamps are powered directly via the central electronic module (CEM) without pulse width modulation.

In Bi-Xenon lamps, the reflector in the lamp housing is moved by an actuator motor when changing between high and low beam. The actuator motor is integrated in the lamp housing.

To detect problems with the low beam, the central electronic module (CEM) reads the power consumption of the circuit. If this falls below a certain threshold value a fault will be indicated. The general warning lamp lights in the driver information module (DIM) and a text message is displayed.

There are diagnostics for the high beam relay.

There are also diagnostics for the high and low beam function (actuator motor) for Bi-Xenon lamps.

Right and left-hand asymmetric lamps

The right and left-hand asymmetric lamps are adjusted mechanically using a simple operation. A lever is accessible when the rear cover on the headlamp housing is opened.

Halogen

Scheme 438

A = left-hand asymmetric

B = right-hand asymmetric

Bi-Xenon

Scheme 439

A = left-hand asymmetric

B = right-hand asymmetric

Scheme 440

There are two motors which angle the headlamps upwards or downwards to control the range of the beam. The motors are integrated in the headlamps.

The motors are controlled by a thumb wheel which is located in the light switch module (LSM) on the dashboard by the side of the steering wheel.

If the thumb wheel is turned, information is transmitted to the motors which adjust the headlamps accordingly.

Scheme 441

There are a number of lamps positioned around the car to mark its position. These are in the headlamps, tail lamps and on the front fenders (US model). The lamps light together with the number plate lighting when the light switch module (LSM) is in parking lamp mode or low beam is on.

The lamps are powered directly via two outputs on the central electronic module (CEM). One of the outputs powers

1. the front left-hand parking lamp
2. the left-hand parking lamps
3. the license plate lighting
4. the rear right-hand parking lamp.

The other output powers

1. the front right-hand parking lamp
2. the right-hand side parking lamps
3. the rear left-hand parking lamp.

There are diagnostics for the light switch module (LSM) and the lamps.

Scheme 442

If the car is equipped with front fog lights, these are in the bumper casing below the headlights.

The fog lamps are operated via a button in the light switch module (LSM). An LED in the button lights when the fog lamps are activated. The light switch module (LSM) is directly connected to the central electronic module (CEM). The lamps are powered via a directly connected relay on the central electronic module (CEM).

There are diagnostics for the fog lamp relay (front).