Variant Coding: Notes

A Variant Code is another means by which market specific application data can be released/assigned to a control module, this process allows one base control module to be utilized for different market applications.

The variant code is a 4 digit hexadecimal (alpha-numeric) code that is entered into a control module as part of the coding process. By entering a valid code into the module a set of operational data (characteristic maps) specific to the code entered is assigned to the operating program of that control module. The operational data and code are semi rigidly assigned, meaning that if a new code is entered, a different set of data is assigned to the program.

Variant coding is only used on engine control modules. Engine control modules which utilize variant coding were first introduced into production vehicles as of 3/87 production with Motronic M1.1 (Engine Control Module ECM/DME).

Variant coding is only used on Engine Control Modules with version M1.X.

ENGINE CONTROL MODULE ECM/DME INFORMATION

DME Version	Series	Cyl.	Engine	Year
M1.1	E28/E30	6	M20/M30	3/87 - 8/92
M1.2	E24/E28	6	S38	87 - 88
M1.3	E34	6	M20/M30	6/87 - 9/90
M1.3	E34	6	M30	6/88 - 12/92
M1.3	E32	6	M30	3/87 - 7/92
M1.7	E30/E36	4	M42	3/90 - 12/93
M1.7.2	E36	4	M42	1/94 - 12/95

Using the DISplus/GT1/SSS with the latest CIP programming software contained within Progman, allows the technician to:

Code a new, uncoded control module.
Recode a previously coded control module.

The variant code is entered into the control module either by:

Adopting the existing code from the defective DME control module (if diagnostic communication is possible).
Manually entering the variant code via the keypad displayed on the screen of the DISplus/GT1/SSS.

Fig 1: Entering Variant Code Into Control Module
Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: M1.X DME control modules can only be coded up to eight (8) times. The GT1/DISplus will display the remaining number of times the control module can be recoded.

If variant coding of an M1.3 control module for an M20 engine is not possible, the cause may be that Pin 18 (DME Code Link) of the 20 pin diagnostic connector may be backed out of the connector preventing communication between the tester and DME control module.