Description Of Modes

Data Output With A Scan Tool, Description


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.


NOTE: The $ symbol means that a hexadecimal number is involved.


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)