Component Tests and General Diagnostics

General Information:





The Yazaki combined instrument panel has a built-in diagnostic system, the Volvo on-board diagnostic (OBD) system, which continuously monitors itself and its input and output signals.

Using the Volvo Scan Tool (ST) it is possible to:
- Read off and erase diagnostic trouble codes (DTCs), counters and frozen values
- Activate gauges according to a predetermined pattern.
- Continuously monitor the value and status of combined instrument panel input and output signals
- Read off control module identification.
- Reset the service reminder indicator (SRI).
- Read off data stored in the combined instrument panel.
- Program the combined instrument panel.





The Scan Tool (ST) and memory cassette make it possible to communicate with the car's various control modules. By connecting the Volvo Scan Tool (ST) to the data link connector (DLC) diagnostic trouble codes (DTCs) can be read and erased, components and functions can be activated, output and input signals can be read, functions reset etc.

Diagnostic Trouble Codes (DTCs):
If the control module detects a fault it will store a diagnostic trouble code (DTC). At the same time the value of 17 predetermined parameters are frozen and stored. These are the frozen values. If the number of diagnostic trouble codes (DTCs) exceeds 5 the frozen values of the 2 first and 3 last diagnostic trouble codes (DTCs) stored are displayed.

The control module can store up to 10 diagnostic trouble codes (DTCs). The first 5 diagnostic trouble codes (DTCs) are stored until they are erased. When the number of diagnostic trouble codes (DTCs) exceeds 10 then new diagnostic trouble codes (DTCs) start to replace diagnostic trouble codes (DTCs) 6-10

Counters:
Every diagnostic trouble code (DTC) has a counter which records the number of cycles which have been fault-free since the diagnostic trouble code (DTC) was stored (intermittent fault). A cycle is started when the following three parameters have been fulfilled.
- Ignition on
- Engine speed (RPM) exceeds 500 rpm
- Vehicle speed exceeds 20 km/h (12 mph)

The cycle is completed when the ignition is switched off.

When a counter is on 0 the control module interprets the fault as permanent. If the counter is greater than 0 the control module interprets it as an intermittent fault. If the fault recurs the counter is reset to zero.

When the counter reaches 255 the diagnostic trouble code (DTC) is erased.