BMW 20-pin Diagnostic Socket Pin-Out Diagram

Handy pin-out diagram for the pre-OBD 20-pin round diagnostic connector on 80s and 90s BMWs from PinOutGuides.com [https://pinoutguide.com/CarElectronics/car_diag_pinout.shtml] 

 

1       Engine rotation speed [TD]
2       CAN-High     
3       CAN-Low
4       Shielding
7       Oil service and Inspection reset    
11     External starter turn on
12     Battery indicator
14     Battery power     +12V
15     ISO 9141-2 L Line     
16     Ignition +12V     
17     ISO 9141-2 K Line
18     Programming line [PGSP]
19     Ground [GND]     
20     ISO 9141-2 K Line [TXD]

 

https://pinoutguide.com/CarElectronics/car_diag_pinout.shtml

BMW Bosch DME Motronic 1.3 Connector / Plug Pinout Diagram

 

Pin Connection

1. 1  ignition coil: t1

2. 2  earth, ignition driver

3. 3  pump relay driver: t85

4. 4  ISCV switching: t1

5. 5  CFSV switching: t1

6. 6  tachometer

7. 7  AFS signal: t2

8. 8  CID signal: t2

9. 9  unused

10. 10  OS return: t4

11. 11  unused

12. 12  AFS supply: t3

13. 13  diagnostic socket : t15

14. 14  earth, injector driver

15. 15  warning lamp (US only)

16. 16  injector pulse, cyls 2 and 4

    (model year 89: cyls 1 and 3)

17. 17  injector pulse, cyls 1 and 3 (model year 89: cyls 2 and 4)

18. 18  battery supply: t30

19. 19  earth, main ECM and shield

20. 20  unused

21. 21  unused

22. 22  unused

23. 23  OS relay driver : t85

24. 24  earth, output drivers other

    than injector & ignition

25. 25  unused

26. 26  AFS return: t5

27. 27  ignition switch: t15

28. 28  OS signal: t3

29. 29  VSS

30. 30  unused

31. 31  CID return: t1

32. 32  fuel consumption meter

33. 33  kick down prevent, AT

34. 34  unused

35. 35  unused

36. 36  main relay driver: t85

37. 37  nbv supply from main relay: t87

38. 38  anti-theft system

39. 39  diagnostic socket : t18

40. 40  A/C pressure switch

41. 41  A/C motor switch

42. 42  AT drive selector

43. 43  CO pot (AFS : t3)

44. 44  ATS (AFS : t4)

45. 45  CTS signal: t2

46. 46  unused

47. 47  CAS: t1

48. 48  CAS return: t2

49. 49  unused

50. 50  unused

51. 51  Ignition timing intervention (Electronic transmission control)

           Note: temporarily switched on during AT downshifts

52. 52  TPS idle contact : t1

53. 53  TPS full-load contact : t3

54. 54  unused

55. 55  diagnostic socket : t20

BMW Bosch Motronic 1.3 DME/ECU: Wiring Diagram + Chip Layout

Diagrams showing the internal wiring structure of the Bosch 1.3 DME electronic control unit for injected BMWs that use it, E30, E28, E34, etc...

High quality PDF - HERE.

Bosch Motronic 1.1-1.3 DME Complete Guide - HERE.

Bosch Motronic Plug Connector Pinouts - HERE.

F10/F11/G07: Front Fog-Lamp / Spot-Lamp Fault fix... the bulb or not the bulb?

 If you get 'Front Foglight Failure' coming up then it's likely a bulb has blown, but I believe it is a common problem on the F10 showing this error but both front fog lamps are still working, or a light not working but the bulb is not blown. It should be an easy fix.

REPLACING THE BULB / CHECKING FAULT:

1. Using an 8mm hex-socket remove four of the screws holding the front side of the corresponding wheel-arch liner - two from the bottom edge and the other two that run up the outer edge of the wheel-arch. This should be enough to peel the arch-liner back and see the back of the fog-light.

2. Remove the wiring-connector by pressing the clip and sliding it upwards.

3. Remove the bulb-holder in the back of the fog-lamp by giving it a quarter-turn anti-clockwise and it should pull out easily.

If the bulb is blown then it can be removed from the plastic holder and replaced.

IF IT'S NOT THE BULB:

The worst case scenario is a fault with the lighting module or wiring to it, see this post - https://www.beemerlab.org/2019/04/f10-halogen-headlight-module-issues.html, but it is far more likely to just be a loose wiring-connector behind the bumper.

Firstly, the wiring-connector to the fog-lamp itself connects from above, so it is possible moisture can fid its way in and corrode the terminals, which can be easily cleaned up with some emery-cloth and a small screwdriver/awl. It is also feasible that road dirt / debris can drop into the plug as it is removed, making it not seat correctly when it is replaced, so rule these out first.

Secondly, there is another wiring connector higher up in the front bumper behind the bottom of the headlight unit. It is hard to spot, as wires seem to run to the fog-lamps from both sides of the car and also link to the headlights, so it will appear as if the wiring to the fogs are intact, when this plug becoming loose or not properly connected will stop the fog-lamp working and throw the error, but not affect the headlights. This can be caused when a headlight has been removed for bulb-replacement or work on the front of the car, so if this work has been done to the car recently then be sure to check this plug. 

E46 318i - Broken Coolant Hose! [11537572158]

 After about 650 miles in the E46 Touring the radiator light came on. Just the amber warning, to let me know it was getting low, not the red warning when it is running out and I refilled about 1.25 litres of water / coolant to the engine. This seemed about right to me, as I feared it may be using a bit of water and there was plenty in when I bought the car so 1.25L in 650 miles isn't catastrophic and can be lived with.
About two weeks later the radiator light came on again and I dutifully refilled 1.25 litres, but the car had only covered 120 miles so I knew something was now amiss, only for the light to come on yet again after just five miles of my six mile round trip to work. Under the hood with the engine running I could see a huge pool of water in the under-tray and a drip, which after much tracing turned out to be coming from a slim rubber hose that connects to the left side of the cylinder-head [N42 engine]. It was a constant drip, but when I wiggled the hose-end the coolant began to spray round the engine-bay, so here was the culprit. Turns out the hose-connector into the head was completely sheared off, as you can see in the pic, and should extend about half an inch into the housing. The only thing holding any water into the upper engine at all was a single M6 thread screw.

The hose in question was BMW Part No. 11537572158, shown in the diagram connecting the thermostat to the cylinder-head. This is a common fault I am told on N42 and N43 engines, along with several other coolant hoses that have plastic end connectors, particularly in the US where kits can be purchased to convert the brittle plastic ends to aluminium ones. This seemed unnecessary for me, given the cost of a replacement part and the age of the car.

As there are so many coolant hose variants, finding the right used OEM one on eBay and the like can be difficult, but they do pop up. I was able to get a new spurious part through work for just £18, but I'm sure commercial motor factors will not be much more expensive as long as they have stock. Spurious hoses tend to come with a new rubber O-ring fitted. BMW dealerships will charge a premium, but at least fitment is guaranteed and they are revised parts, though these may not come with the rubber O-ring which will also need to be ordered.