Diagnostic Functions

Diagnostic functions

General
The central electronic module (CEM) is the main unit for the headlamp levelling and active headlamp functions. In the control module are diagnostics for the functions. For information about diagnostic functions, see Design and Function, central electronic module (CEM).
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 which are detected are defined as intermittent. An operating cycle involves ignition on and off.

Reading and erasing diagnostic trouble codes (DTCs)
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.
For more information about parameters, see Vehicle communication information in Specifications, other.

Activating components
This function can be used to activate components to check that they are working.
For more information on activations, see Vehicle communication information under Specifications, other.

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:
- hardware P/N (control module without software)
- hardware serial number (control module without software)
- software P/N
- diagnostic software P/N (part of the software).