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Discussion Starter #1
The latest version of the PC Software for the GS-911 Diagnostic Tool has additional functionality for the LT Engine ECU, including "TPS Adjustment". It looks like it cycles the throttle positioner, then pauses for you to set the potentiometer and re-test. Their website and documentation has no details on this procedure.

The Clymer manual is also mum on any procedures concerning the throttle positioner or potentiometer - it just says (p. 253): "Replacement and adjustment of these components requires the BMW MoDiTeC unit". I'm assuming the procedure would be similar or identical to the "official" procedure, but I can't find that anywhere.

My problem is this: My '05 LT was stumbling badly off of idle, and occasionally quiting when coming to a stop after an extended period on the road. After borrowing a GS-911, I determined that the O2 sensor was out of spec, so replaced it last week. (And, bought my own GS-911). I disconnected the battery overnight, then reset the TPS after reconnecting, and everything was good for awhile - idle still a bit low, though. Riding yesterday, the engine quit every time I came to a stop - it won't idle at all once warmed up.

I've got the battery disconnected right now, and will try again this evening. But if I still have a problem, I'd love to know: Can I adjust the TPS potentiometer, and how?
 

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ghannah said:
I disconnected the battery overnight, then reset the TPS after reconnecting, and everything was good for awhile - idle still a bit low, though.
How did you reset the TPS?
 

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Glyde,
Your post is timely for me. I am having idle problems (high) and I am showing a tps fault on the GS911. Was about to spend some time going through the adjustment procedure. Not sure if the tps is bad or just misadjusted. I'll hold off if the pot has to be adjusted and can only be done by the Moditec. I have tried the throttle twist adjustment to no avail. You might post your question on the GS911 forum as well.

Bob
 

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Discussion Starter #4
wrmoss said:
How did you reset the TPS?
By "reset" I meant the procedure to train the motronic after it has been unpowered for awhile:
1) Turn the switch to ON (don't start the engine)
2) Turn the throttle from fully closed to fully open at least twice (I do it 3 times)
3) Turn the ignition switch to OFF.
4) Start the engine normally, but without touching the throttle
5) Once warmed up, go for a short ride.
 

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ghannah said:
By "reset" I meant the procedure to train the motronic after it has been unpowered for awhile:


1) Turn the switch to ON (don't start the engine)

2) Turn the throttle from fully closed to fully open at least twice (I do it 3 times)
3) Turn the ignition switch to OFF.
4) Start the engine normally, but without touching the throttle
5) Once warmed up, go for a short ride.


Okay, as far as I know (and my knowledge is limited) that is the correct procedure. Probably have to wait until the weekend is over to get the real experts to weigh in...
 

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wrmoss said:
Okay, as far as I know (and my knowledge is limited) that is the correct procedure. Probably have to wait until the weekend is over to get the real experts to weigh in...
I'm not the real expert, butt that is the correct procedure - and it's in the booklets that come with new LTs (or at least used to!). Only thing different I do, is NOT let the bike warm up - just start it up and hit the road. That is also in the booklet! ;)
 

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Discussion Starter #7 (Edited)
Retraining the Motronic for throttle position didn't help. Cold idle is good - about 1100 rpm. But as the engine warms up idle drops. Above about 190 degrees F idle is below 600 rpm, then the engine quits. Throttle response is glass-smooth, though.

I did get a response on the GS-911 forum. Evidently the software will step you through the procedure, including removal of the idle actuator and tweaking of the Throttle position potentiometer. So it's tupperware time again. Too hot to ride, anyway.
 

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thanks for keeping us posted on your progress.
One of the sensor inputs to the motronics is engine temperature. I wonder if that is causing your headache. My idle is running high and I'm seeing a GS911 fault code for the TPS. I'm leaning towards bringing it to the dealership for service. I just don't want to get her stripped down only to find I can't resolve the problem.

Bob
 

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Discussion Starter #9
Bob,

I had the opposite problem - after warmup, idle speed went to 0. But everything seems good, now. I have successfuly gone through the TPS adjustment procedure as spelled out by the latest version of the GS-911 software. The procedure is easy; getting access to the throttle position actuator and sensor takes awhile, though. First, run the first part of the TPS Adjustment test to be sure the potentiometer needs to be adjusted. If the upper bar is red, you'll need to get to the throttle body rail to proceed.

In a nutshell, you have to get to the throttle bodies by removing the black and chrome "wing covers", upper left and right tupperware, stingray, seat support, and fuel tank. Try to remember where all of the plugs go. If you're organized and have done this before, it takes about 90 minutes. You can then run the second part of the test, which requires removing the throttle position actuator - the unit that looks like a small windshield washer motor on the side of the throttle body rail. If this step fails (upper bar is red), you'll need to adjust the potentiometer.

So loosen the clamps securing the intake tubes to the airbox and pull the airbox to expose the throttle bodies. Then, loosen the left radiator by pulling the mounting clips and angling it forward a couple of inches, and remove the bolts holding the injector rail so that you can pull the injectors out. No need to disconnect anything. Finally, loosen the bottom clamps securing the throttle bodies to the head and slide the throttle bodies up and forward to expose the potentiometer on the back end of the throttle body rail. Loosen the two screws enough to turn the pot to center the upper bar in the GS-911 software, and follow the directions onscreen to lock it down and verify. They will also direct you to remount the actuator and re-test.

You're done! All you have to do now is remount the throttle body rail, injector rail, airbox, radiator, gas tank, seat brace, and tupperware!

Yes, this'll keep you busy for awhile. But the new GS-911 software finally makes it possible to do something that we would have had to pay a dealer through the nose to do for us if we're out of warranty. The bike's idling great now, with smooth response right from idle. But check your O2 sensor first - it's a lot easier to get to!

- Glyde


drifter36 said:
thanks for keeping us posted on your progress.
One of the sensor inputs to the motronics is engine temperature. I wonder if that is causing your headache. My idle is running high and I'm seeing a GS911 fault code for the TPS. I'm leaning towards bringing it to the dealership for service. I just don't want to get her stripped down only to find I can't resolve the problem.

Bob
 

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I'm coming up on a 36k checkup so I think I'll do the TPS along with the rest. I've had the stingray and all the tupperware off, Dealer did that last fuel/air filter changeout. So I think you've given me enough confidence to try it. Doesn't sound to difficult, mostly time consuming.
The bike is not running too badly. Mostly high idle and reduced gas mileage. Replaced the O2 sensor but made no difference.

I'll need to refer back to your detailed comments. Thanks Glade.

Bob
 
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