S40 T5 AWD L5-2.5L Turbo VIN 67 B5254T7 (2008)
Headlamp Control Module: Initial Inspection and Diagnostic Overview
Headlamp Control Module (HCM)
Diagnostic functions
General
The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output
signals.
Diagnostic trouble codes (DTCs)
A diagnostic trouble code (DTC) is stored if the control module detects a fault.
A fault which is detected in the most recent operating cycle is defined as permanent. Other faults are defined as intermittent. An operating cycle involves
ignition on, the vehicle speed exceeding 20 km/h and the ignition being switched off.
Reading out and erasing diagnostic trouble codes
Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.
Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.
Reading off input and output signals
This function can be used to continuously read off the status of the control module's input and output signals. Activating components This function can
be used to activate components to check that they are working.
Reading off the control module identification
The diagnostic tool identifies control modules by reading off a number of codes from the control module memory.
The codes contain the following information about the control module:
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hardware P/N (control module without software)
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hardware serial number (control module without software)
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software P/N
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diagnostic software P/N (part of the software).
