Non-Standardized Serial Communication

As a supplement to Volvo Diagnostics - first and second version, the supplier of engine management systems developed their own diagnostic and communication methods (On Board Diagnostic). These were introduced during 1991/92  .

These serial* communication methods were supplier-specific and varied a lot between systems. To communicate quickly and directly with control modules was a pre-condition for developing the control system and opened for new possibilities.

The access to more information about the detected problem as well as the possibility to, e. g., quickly read out parameters, enabled improvement of troubleshooting methods. Therefore, these communication methods were used by the workshops' diagnostics tools.

The cable in the vehicle used for this serial communication is connected to the diagnostic socket in the engine compartment and is the same one used for Volvo Diagnostics, first and second version.

Included functions are, among others: 

• Reading out and erasing diagnostic trouble codes.
• Reading off frozen values.
• Reading off values of signals such as coolant temperature, voltage on heated oxygen sensor, etc.
• Activating components and functions.
• Programming of customer parameters and functions.
• Calibration of functions.
• Resetting of adaptations.

The tool Volvo System Tester was developed to make communication easier with the control module.

Non-standardized serial communication was introduced on engine management system Motronic 1.8 in model 960 and engine management system Fenix 5.2, Motronic 4.3, and LH3.2/EZ129K in model 850.

*Serial means that the information is sent as a series of signals in the form pulse trains (= series of pulses) via a cable between the tool and control module.