ODB2 on a 1999 BMW Z3 2 liters

Subject : Trying to connect an OBD2 diagnostic tool on my Z3;

Getting some errors when trying to connect to IKE and EWS.

The BMW diagnostic connector, 20 pins,  under the hood.

used in all BMW models in 1988-2000's

   

Pin	Signal	Description
1	Engine rotation speed	TD
2	OBD-II diagnostic
7	Oil service and Inspection reset
11	External starter turn on
14	Battery power
15	ISO 9141-2 L Line	RXD- Diagnostic Data link
16	Ignition +12V
17	ISO 9141-2 K Line	TXD II - ODB2
8	PGSP	Programming line
19	GND
20	ISO 9141-2 K Line	TXD - Diagnostic data link

The specific BMW OBD-II pinout in the car :

used in all BMW models produced after 2000's

   

Pin	Signal	Description
1	+12V	Ignition(in run or start)
4	CGND	chassis ground
5	SGND	Signal ground
7	ISO 9141-2 K-LINE	engine (ISO-9141 and ISO-14230), automatic transmission diagnostic (in some models) TXD II
8	ISO 9141-2 K-LINE	IKE/KOMBI, ABS, ABS/ASR, ABS/ABD, ESP, DSC, Airbag and other electronic equipment (AFTER 2001 ) TXD
9	TD/RPM	Engine rotation speed
16	+12v	Battery power

   

For BMW cars before 2001 having the OBD2 DLC in vehicle, as  shown on the above figure, it is not possible to acces the IKE, EWS, ABD, and maybe others modules because the “TXD” is not connected to the OBD2 plug.

Note that you need to close the cap of the 20 pins diag connector to establish the connection between TXD II and the OBD plug (the #17 and # 2 are connected when the cap is closed).   

If you are using some tools like BMW scanner, you will only be able to read the DME module, most of the time.

To enable the reading of all module FROM THE OBD2 in the vehicule, you have, with a thin wire, to brigde the 17 TXDII and 20 TXD and 2 on the 20 pins diag connector, or only bridge 17+20 and close the cap if the wire is thin enough.    Then, IKE, EWS and other modules become accessibles.