BMW 745i Motronic Interconnections - Transmission side

These interconnection numbers refer to the connection numbering in the "Transmission wire harness overview" and to the schematic diagram.
If you use this information with both overviews and the schematic diagrams you have quite complete picture of the whole engine and transmission management system. Many non-745i owners have asked for this information as they plan to install 745 engine into their car and sometimes also want to use or modify existing wire harness instead of 745i original. Some also want to use the 745i engine with manual transmission.

Some notes about manual transmission with M102 (745i) engines:

First of all I want to make my point clear: I do not recommend to use manual transmission with the Motronic 3.4 L turbo engine. I admit that it has some benefits mainly in the "fun department" in burning rubber etc...(you can burn rubber also with the automatic tranny with the benefit of not burning the clutch). However, manual transmission will not give faster acceleration with this engine eventhough people usually think so.
When BMW designed the 745 car they had valid reasons to offer it with automatic transmission only: Motronic is able to lower the power for the short time during shifting with the help of the 2.1 torque converter. This lowers the stress of the power chain to the rear wheels considerably and enables long term reliability. BMW did not have powerful enough manual tranny to go with M102 engine. Key point for good acceleration is constant turbo boost. With manual tranny you loose the high turbo pressure every time you engage the clutch and release foot throttle. Furthermore there is one extra main disadvantage for manual transmission in the mechanical construction of the intake system: When you release the foot throttle fast for switching you suddenly close the butterfly valve and all that pressurized air hits the "wall" with no place to go but back to the turbo slowing it down even faster. This creates very high pressure to the intake chain and usually one of the weakest links (any of the rubber hoses) will break.
Note that this was not a problem with the 3.2 L L-Jetronic M102 engine because that engine has a special by-pass valve to release such peak back boosts. Ideally, one should combine that part of the intake system to the 3.4 L engine.
All above points are multiplied when you use higher than factory boost levels.
Let me give you an real example: One guy ordered our chip upgrade for his 5-series car with M102 engine and clutch/tranny assembly from a M6. He was burning rubber at approx. 1 bar boost (14.5 PSI) for about 1 minute when he burned his clutch completely. Still today this is the first and only complaint I've ever had on my chips. He called me laughing saying that I should have included US style warnings what to do or not to do with the engine (well, that would be quite a challenge). Anyway, he bought new clutch and learned his lesson. Seriously, you should use copper clutch if you use manual tranny with M102 engine.

A lot better way to make 745i car "manual" is a "Steptronic" type of system like e.g. "J-Tronic" which is just our concept for ZF 4HP22-EH Automatic Transmissions. With this kind of system you combine all the good points of manual transmission with those of an automatic transmission. Shifting times are very fast with no lag or no loss of turbo boost.
The J-Tronic system might include small box with numeric display for gears, switch between normal and J-Tronic modes, Green LED for "J-Tronic Active" , yellow LED for optimum shifting point and Red LED for RPM limit.
The system can be activated only when gear shift lever is at "D" with drive program "E". Only gears 1-4 are possible to select with the "+" and "-" buttoms. Deselected with either the "J-Tronic Switch" or by moving the gear shift lever from "D".
Please go to the "Poll" section to give your opinion of this proposed system. Like I said this is still a concept and may or may not be a real product.

For all of you who still want to or have to use manual transmission with the M102 engine here are the modification instructions:

1. Short circuit Relay K1 as instructed in the "Transmission Overview".
2. Remove transmission cable from the Motronic box
3. Remove Relay K2 from it's socket
4. Remove 4-pin connector "B" between Motronic engine and transmission wire harnesses.

This is the easiest way to do it. There are other ways to do it which may seem better. We do not have such a car to do real tests, but based on our simulations, knowledgement of each wire connection and schematic diagrams of inside Motronic Box I think we are right.

 


BMW Drawing no: X12* Motronic 0261 200 013 * Transmission Socket *
Pin no: Interconnection numbers Connected to: Wire colors:
X12.1 NC No Connection

X12.2

X11.B Transmission socket for valve Y5 Red
X12.3 S4 Kick down switch Grey Yellow
X12.4 X8.E E in "S, E, 321" selector switch Brown Red
X12.5 X11.H Transmission socket for valve Y4 Orange
X12.6 X11.K Transmission socket for valve Y3 Green
X12.7 X11.D Transmission socket for valve Y2 Grey
X12.8 X11.F Transmission socket Brown
X12.9 NC No Connection
X12.10 K2.86 Terminal 86 of Relay K2 White
X12.11 NC No Connection
X12.12 X7.9, X6.11 Gear shif lever connector for gear 1, Dashboard pin 11 Blue Red
X12.13 X7.8, X6.10 Gear shift lever connector for gear 2, Dashboard pin 10 Blue Black
X12.14 NC No Connection
X12.15 NC No Connection
X12.16 NC No Connection
X12.17 X11.L Transmission socket for valve 1 Blue
X12.18 X11.M, K2.87 Transmission socket + 12V, Relay K2 Violet
X12.19 K2.85 Relay K2, terminal 85 Brown Yellow
X12.20 NC No Connection
X12.21 NC No Connection
X12.22 - Ground Brown
X12.23 - Ground shield for transmission socket wires Shield
X12.24 NC No Connection
X12.25 NC No Connection
X12.26 NC No Connection
X12.27 X11 Transmission socket White
X12.28 X7.10, X6.9 Gear shift lever connector for gear 3, Dashboard pin 9 Blue Grey
X12.29 X7.7, X6.8 Gear shift lever connector for gear D, Dashboard pin 8 Blue Green
X12.30 X7.6, X6.6 Gear shift lever connector for gear N, Dashboard pin 6 Blue Brown
X12.31 X10.2 Pin 2 of 4-pin connector to engine wire harness White Blue
X12.32 X10.3 Pin 3 of 4-pin connector to engine wire harness White Red
X12.33 NC No Connection
X12.34 X8.321 321 in "S, E, 321" selector switch Brown White
X12.35 X10.4 Pin 4 of 4-pin connector to engine wire harness White Yellow

 



* BMW Drawing no: K2*Transmission Relay * (next to front right loudspeaker)
Number: Interconnection numbers Connected to: Wire colors:
K2.30 X10.1, K2.86 Connector to engine wire harness Red Blue
K2.85 X12.19 Motronic connector pin 19 Brown Yellow
K2.86 X12.10, X10.30 Motronic connector pin 10 White
K2.87 X12.18, X11.M Motronic pin 18, Transmission +12 V Violet
K2.87a X6.1 Dashboard connector pin 1 Red White
Note: Relay 966 (engine wire harness) feeds 12 V supply to K2.30.
* BMW Drawing no: X10* 4-pin connector to engine wire harness*
Number: Interconnection numbers Connected to: Wire colors:
X10.1 K2.30, K2.86 Relay K2 Red Blue
X10.2 X12.31 Motronic pin 31 White Blue
X10.3 X12.32 Motronic pin 32 White Red
X10.4 X12.35 Motronic pin 35 White Yellow
* BMW drawing no: X11* 8-pin connector to transmission *
Number: Interconnection numbers Connected to: Wire colors:
X11 X12.27 Motronic pin 27 White
X11.F X12.8 Motronic pin 8 Brown
X11.L X12.17 Motronic pin 17, Valve Y1 Blue
X11.M X12.18, K2.87 Motronic pin 18, Relay K2.87 Violet
X11.D X12.7 Motronic pin 7, Valve Y2 Grey
X11.K X12.6 Motronic pin 6, Valve Y3 Green
X11.H X12.5 Motronic pin 5, Valve Y4 Orange
X11.B X12.2 Motronic pin 2, Valve Y5 Red
* BMW Drawing no: X8* S, E, 321 Program Selector*
Number: Interconnection numbers Connected to: Wire colors:
X8.E X12.14 Motronic pin 14 Brown Red
X8.321 X12.34, X6.3 Motronic pin 34, Dashboard X6 Brown White
* BMW Drawing no: S4* Kick Down Switch*
Number: Interconnection numbers Connected to: Wire colors:
S4 X12.3 Motronic pin 3 Grey Yellow
* BMW Drawing no: X7* Gear Shift Lever*
Number: Interconnection numbers Connected to: Wire colors:
X7.1 - Ground Brown
X7.2 K1.85 Relay K1.85 Brown Black
X7.3 X6.12 Dashboard connector pin 12 Green Black
X7.4 ("P") X6.4 Dashboard pin 4 Blue Yellow
X7.5 ("R") X6.5 Dashboard pin 5, back up lights Blue White
X7.6 ("N") X6.6, X12.30 Dashboard pin 6, Motronic pin. 30 Blue Brown
X7.7 ("D") X6.8, X12.29 Dashboard pin 8, Motronic pin 29 Blue Green
X7.8 ("2") X6.10, X12.13 Dashboard pin 10, Motronic pin 13 Blue Black
X7.9 ("1") X6.11, X12.12 Dashboard pin 11, Motronic pin Blue Red
X7.10 ("3") X6.9, X12.28 Dashboard pin 9, Motronic pin 28 Blue Grey
* BMW Drawing no: X6 * Dashboard Connector*
Number: Interconnection numbers Connected to: Wire colors:
X6.1 K2.87a Relay K2 Red White
X6.2 - Ground Brown
X6.3 X8.321 E,S,321 Selector Brown White
X6.4 X7.4 ("P") Gear Shift Lever pin 4 Blue Yellow
X6.5 X7.5 ("R") Gear Shift Lever pin 5, back up lights Blue White
X6.6 X7.6 ("N"), X12.30 Gear Shift Lever pin 6, Motronic pin 30 Blue Brown
X6.7 X6.6
X6.8 X7.7 ("D"), X12.29 Gear Shift Lever pin 7, Motronic pin 29 Blue Green
X6.9 X7.10 ("3"), X12.28 Gear Shift Lever pin 10, Motronic pin 28 Blue Grey
X6.10 X7.8 ("2"), X12.13 Gear Shift Lever pin 8, Motronic pin 13 Blue Black
X6.11 X7.9 ("1"), X12.12 Gear Shift Lever pin 9, Motronic pin 12 Blue Red
X6.12 X7.3 Gear Shift Lever pin 3 Green Black
* BMW Drawing no: K1 * Relay K1*
Number: Interconnection numbers Connected to: Wire colors:
K1.30 S1.50 Ignition Switch pin 50 Black
K1.85 X7.2 Gear Shift lever pin 2 Brown Black
K1.86 K1.30   Black
K1.87 M1.50 Starter Black yellow
This relay is located under the dashboard left from steering shaft. It is usually connected on right side of a white connector.
Special note for those who want to use manual transmission: Either remove the relay and connect terminals 30 and 87 together or keep the relay in the socket and connect terminal 85 permanently tp ground.