Data output with a scan tool: Notes

The output of data relevant to OBD from the control modules was stipulated by law for the USA. It is described in SAE J 1979.

Data output is subdivided into different modes.

Mode 1 

Output of:

• Input signals
• Output signals
• System status information
• Values calculated by the control module

Mode 2 

Output of operating conditions (Freeze Frame), if a fault has been stored.

Mode 3 

Output of stored faults.

Mode 4 

Erase the fault memory.

Mode 5 

Output of oxygen sensor data.

Mode 6 

Output of test results of non-continuous tests.

Mode 7 

Output of test results of continuous tests.

Output of suspected faults.

The data sets in the modes are referred to as Parameter Identification (PID).

After being stimulated by a generic scan tool, all systems relevant to OBD log on with their address. In vehicles with ME 7.8, this is the DME with the address $11 and in Tiptronic vehicles it is the transmission control module with the address $1A.

When the control module provides data, it also states the mode, the PID number and the address of the control module.

For example:

Mode 41 PID $01 address $11

Engine control

Number of faults: 0

Check Engine: off

The output of data is carried out:

in Mode 1 with Mode 41,

in Mode 2 with Mode 42,

in Mode 3 with Mode 43, etc.

Mode 8 

Activation of drive links (is not supported)

Mode 9 

Output of vehicle information (as of model year 2002)