lundi 18 janvier 2016

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.
20 pin car OBD2 proprietary of BMW OBD II  vehicle diagnostic connector connector layout
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 :

16 pin J1962 OBD-2 car proprietary of BMW OBD-II diagnostic interface connector layout
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.




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