Fault Tracing With Volvo Scan Tool (ST)

C. Fault tracing with Volvo Scan Tool (ST)

CA. General






Applications

The ST offers a faster means of performing fault tracing on the MFI and Dl systems. The instrument is used in most of the fault-tracing procedures and provides more fault information than has been possible until now.

Communication with control modules

Connecting the ST to the vehicle diagnostic system enables the instrument to communicate with the MFI and Dl systems in two ways:

Firstly, the ST can communicate with the control module memory in the serial mode. Apart from reading DTCs, this enables the instrument to determine if the fault is intermittent or permanent, and if the signal causing the DTC is too high or too low, or is not present. Serial communication also enables the ST to read the values of various operating parameters (Monitor test) and to memorise these values (Freeze test function).

The instrument can also be used with Volvo Diagnostics, in which case it performs the same functions as those activated when using DLC A - reading and erasing DTCs, acknowledging component operation (DTM 2) and activation of components (DTM 3). (DTM - Diagnostic Test Mode)

Both types of communication are feasible with the ignition on or with the engine running, with the following exceptions:

Operation of components (DTM 3) is possible only with the ignition on and engine off.
In the case of MFI modules on 1992 models and some 1993 models, serial communication is possible only when the engine is running. When reading MFI DTCs without starting the engine, the ST instead communicates with the control modules through Volvo Diagnostics.

Principle of operation






The ST can read DTCs and display the values of input and output signals. In addition, previously inaccessible quantities, such as adaptive values, can be read and the instrument also enables the user to determine whether a fault is intermittent or permanent.

Since the ST reads directly from each control module memory, all values are the same as those interpreted by the control modules themselves. This, together with the fact that the user does not need to encroach on the system, for example, to disconnect connectors for measurement purposes, makes fault tracing both faster and more reliable.

System identification

The ST identifies the appropriate control module by reading a code in the memory, enabling it to display the parameters relating to that module.

Key functions






In most cases, the functions of the keys are as described below.
Pressing an undefined key will produce a long bleepin~ signal.

ENTER: Activates selected function and displays next menu.

EXIT: Displays a previous menu or interrupts a function.

YES/NO: Used to answer prompts and to add or delete parameters.

Up/Down Arrows: Used to select menu options e.g. to move the cursor or to display text or values which are not visible in the display window.

HELP: Provides information on key operations relevant to the menu displayed when the key is pressed. See example.

Example of Help menu






Four lines are displayed at a time. Use the arrow keys to scroll up and down through the menu. Press EXIT to exit menu.

Three main functions

This provides a more detailed display ot the main function and related sub-functions:

CD. Diagnostic test
CE. Monitor test
CF. Freeze test function