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DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSVOLVO2009XC70 BASEREPAIR AND DIAGNOSISENGINE PERFORMANCEENGINE CONTROL SYSTEMSELECTRICAL MODULES AND COMPONENTS - DESIGN AND FUNCTION - 3 OF 5HEADLAMP CONTROL MODULE (HCM) (2010-2011)SYSTEM OVERVIEWSIGNALS

2009 Volvo XC70 Base

System Overview: Signals

2009 Volvo XC70 BaseSECTION Signals

The table below summarizes the input signals to and output signals from the headlamp control module (HCM). The signal types are divided into directly connected signals, serial communication and CAN communication. The illustration below displays the same information with the Volvo component designations.

Input signals	Output signals
Directly connected:	Directly connected:
Position sensor (7/119, 7/121)	Motor, headlamp levelling (not active headlamps)
Via serial communication:	Via serial communication:
Left headlamp control unit (LHCU)/Right headlamp control unit (RHCU) (vehicles with active headlamps only)	Left headlamp control unit (LHCU)/Right headlamp control unit (RHCU) (vehicles with active headlamps only)
Via Controller Area Network (CAN) communication:	Via Controller Area Network (CAN) communication:
Suspension module (SUM) (4/84) Transmission control module (TCM) (4/28) Brake control module (BCM) (4/16) Engine control module (ECM) (4/46) Steering wheel angle sensor module (SAS) (3/130) Infotainment control module (ICM) (3/281) Central electronic module (CEM) (4/56)	Driver information module (DIM) (5/1) Infotainment control module (ICM) (3/281)

Fig 1: Identifying Input Signals To And Output Signals From Headlamp Control Module (HCM)

Courtesy of VOLVO CARS CORPORATION

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.