After 10 seconds Googling the following (Dutch one) but lots of also US/UK-stories in the Interweb.
(You do have Motronic MA 2.4 in LT)
Also after 20 seconds in the google following info how to read fault codes:
"Firstly you can do some investigation of your own fault codes. Under the front seat and clipped to the frame there is a diagnostic connector. It is cylindrical in shape and has a removable push-and-turn gray cap.
Remove the cap and locate the pin 2, connected to a brown/blue wire. Connect an analogue meter between pin 2 and earth. Turn on the ignition. The meter will initially settle at around 10V. It's what happens next that is of interest. The needle will fall to a number of lower voltages in a series of pulses. Count the number of needle drops. This number is your fault code.
I do have gs911 so haven't needed to do it manual way. I have bumped numerous times in the net for the ECU-fault codes, so spend some time searching and you will be rewarded...
I would start solving the problem by disconnecting the intake air sensor and seeing if that makes any difference. In early models (99 - 2002 or something?) that caused just those symptoms you described. I have disconnected mine (99-LT) just for the same reason... Depending on the model/year there are different ways to approach this problem. Look for the "brown wire" and read few threads....
Ok.... Some more story copied with proud from ADVRIDER Forum
Reading the Fault Codes on the R1150
First of all credit where credit is due…..http://www.bmwgsclub.nl/motronic-reset.html which I got google to translate to English – not perfect but enough to get the jist that the 1150 MA 2.4 can be read in a similar way to the 1100 MA 2.2.
I tried the LED method and it did not work, the impedance was too low.
Next I tried my DVM and lo and behold I got the first hall sensor code 1133, I then prompted the next code and got 1122 (both these codes come up if the engine is not turned over or running) The next prompt was 1111 which I expected as there is no cat code plug on my bike followed by 0000 – no further faults.
I then disconnected the temp sensor on the air cleaner and got 1223 Engine temp sensor fault. Pulling Fuse #5 for at least 1 min reset that fault.
So in a nutshell, reading the MA2.4 is similar to the 2.2 if you use a high impedance 200k or better Analog meter or DVM with a bar graph if you bring out pin #18 from the Motronic. Note: too low impedance a meter will cause the Motronic to try to prompt the next fault code and not report.
NOTE: IF YOU ARE NOT TOTALLY COMFORTABLE WITH ELECTRICAL MODIFICATIONS READ NO FURTHER. ALL MODIFICATIONS ARE AT YOUR OWN RISK. CONSULT AN EXPERT IF YOU HAVE ANY DOUBTS IN YOUR ABILITIES.
Follow the procedure on page 71 of Carl Kulow & co IBMWR http://www.ibmwr.org/r-tech/oilheads/index.shtml to extract the codes just as you would on the R1100 the only difference being instead of referencing Pin 1 of the diagnostic connector you will use the wire brought out from pin #18 of the Moditec as below
The mod to the machine is as follows:
Remove the tank and disconnect the battery
Unscrew the 4 bolts holding the Motronic and undo the connector
Carefully peel back the boot and disassemble the connector exposing the wires on the inside.
Locate Position #18 at the end (no wire exists) – that’s where you will be adding a new wire and crimp. (I went to my local auto wrecker and got a compete connector to rob crimps from off a mid ‘90s BMW 320 to match the ones on my GS)
Cut a suitable length of wire, solder a salvaged crimp and insert into position #18 (purple plastic lock strip must be removed to do this, be sure to replace)
Reassemble the connector assembly routing the new wire out through a pierced hole in the rubber boot.
Continue to route the wire to an conveniently accessible location ( I brought it alongside the existing diagnostic plug) and attach an insulated connector of your choice that will accept a meter probe. Be sure to avoid any sharp edges.
Snap connector back on the Motronic and replace 4 screws not forgetting the ground wire on the left bottom side.
Reconnect the battery and replace the fuel tank.
Turn ignition switch on and open throttle wide open twice. (to reset TPS signal to Motronic)
Some pictures below to clarify the procedure.
BTW: Given the choice I prefer my analog meter - it is easier to read the 'dips'
Aaaaand some fault codes:
1111 CO potentiometer not detected with Oxygen sensor disconnected
1122 No signal from Hall Sensor #1 (Upper or TDC Sensor, Coil 1/4)
1133 No signal from Hall Sensor #2 (Lower or 180į Sensor, Coil 2/3)
1215 Throttle Position Sensor out of range
1223 Water Temperature Sensor out of range
1224 Air temperature Sensor out of range
2341 Oxygen sensor at limit
2342 Oxygen sensor signal invalid
2343 Mixture setting at limit
2344 Oxygen sensor shorted to ground
2345 Oxygen sensor shorted to 12V
3333 Fan Test in Progress (the fan motor will run intermittently and
the 3333 code will flash)
4444 No fault stored