XC70 AWD L6-3.2L VIN 98 B6324S (2009)
A control module is mounted beneath each lamp housing on vehicles with active headlamps.
The left headlamp control unit (LHCU) and right headlamp control unit (RHCU) handle headlamp levelling and active control of the light beam. Active
control means that the light beam is turned out to the left or right. The light beam is turned out at varying degrees and rates depending on vehicle speed
and steering angle.
Information is transferred between the left headlamp control unit (LHCU), right headlamp control unit (RHCU) and headlamp control module (HCM)
via serial communication.
The lamp housing contains a sensor that indicates whether the light beam has been turned out to the right or left. The left headlamp control unit (LHCU)
and right headlamp control unit (RHCU) send this information to the headlamp control module (HCM).
If there is no communication with the headlamp control module (HCM) or there is a fault in the left headlamp control unit (LHCU) and/or right
headlamp control unit (RHCU), headlamp levelling and active control are disabled. The light beam then assumes its "limp-home" position.
The left headlamp control unit (LHCU) and right headlamp control unit (RHCU) can be diagnosed.
High voltage unit
High voltage is required to light the Bi-Xenon lamp.
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A high voltage unit is connected to each Bi-Xenon lamp. This transforms 12-V voltage to the approximately 24,000 V required to light the lamp.
Once the lamp is on, voltage is lowered to the approximately 100 V required to keep the lamp lit.
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Each time voltage is supplied to the high voltage unit, an attempt is made to light the Bi-Xenon lamp. If this voltage does not exceed 9.5 V during
a time period of 200 ms, the lamp does not light. If voltage is too low, such as after a voltage-consuming cold start, the lamp does not light just
because the engine is running and the alternator begins charging. A new attempt must be made to start the lamp by turning the light switch to the
"0" or parking light position and then back to the low beam position.
Warning! Because of the high voltage it is important to follow the instructions for working with Bi- Xenon lamps and the high voltage unit!
