Description of On-Board Diagnostics

Diagnostic functions

General

The control module has an on board diagnostic system, Volvo Diagnostics. The control module continuously monitors itself and input and output signals in the system. By connecting the Volvo Scan Tool (ST) to the data link connector (DLC) it is possible to obtain different types of information in the form of diagnostic trouble codes (DTCs), current parameters for readings on components etc.

The diagnostics system can also be used to activate components and functions by using the Volvo Scan Tool (ST).

NOTE: If it is not possible to operate the seat or access the diagnostic system, check that none of the buttons on the control panel are stuck in the down position. Carry out the procedure again with the engine of the car running. Battery voltage must be at full voltage in order for the before the on-board diagnostic (OBD) system to work. Refer to Checking supply voltage and Checking communication

Diagnostic Trouble Codes (DTCs)

If the control module detects a fault it is stored as a diagnostic trouble code (DTC). In all 23 diagnostic trouble codes (DTCs) can be detected and stored. The control module can store up to 8 diagnostic trouble codes (DTCs) at any one time.

When a diagnostic trouble code (DTC) is stored, values for a number of pre-determined parameters are frozen. The frozen values can be used to read out, for example, what the control module has registered regarding the position of the control buttons or the value from a potentiometer when the fault occurred.

For each diagnostic trouble code (DTC) there is a counter, counter 2, which provides the total number of cycles completed without a fault since the diagnostic trouble code (DTC) was stored.

A cycle begins every time one of the buttons on the control panel is pressed. Where a counter counts when a button is pressed there is no fault at that particular moment in time. This function can be used to determine if a fault is permanent or intermittent.

After all diagnostic trouble codes (DTCs) have been read off and the necessary repairs made they must be erased. The seat can then be tested, following which a new reading of diagnostic trouble codes (DTCs) should be made to verify that the fault has been corrected.

One diagnostic trouble code (DTC) PSL/PSR-424 is, however, permanent and cannot be erased.