Throttle stops working - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 9 (permalink) Old 05-20-2019, 08:55 PM Thread Starter
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Throttle stops working

Hi,

I have a 2015 and the throttle stops working while the bike remains running. When this happens, the yellow light on the instrument cluster comes on. I can cycle the key to get it to start working again. I changed the throttle assembly and it still happens at random. I read the threads on this site and didn't see anyone with a solution.

I don't see anything apparent in the wiring and wiggling the connections doesn't trigger the failure. The codes I get include "21F950 throttle grip sensor, comparing error..."

Anyone have and solve this issue?

Thanks
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post #2 of 9 (permalink) Old 05-20-2019, 09:18 PM
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1. Reset throttle adaptations and see if it fixes it
2. Inspect twist grip connector to make sure its not loose. Use a magnifying glass to inspect pins and make sure they are not widened or backed out
3. Replace the twist grip connector
4. Can also replace wiring harness to twist grip. There is a part number for just that part
5. Sensor on throttle body or the unit itself.

Common problem. It's one of the 5 things above. Did you replace the twist grip housing on the handlebar or the actual throttle body and or sensors?
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Last edited by bennymx; 05-20-2019 at 09:20 PM.
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post #3 of 9 (permalink) Old 05-20-2019, 10:13 PM
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Quote:
Originally Posted by prev1 View Post
Hi,

I have a 2015 and the throttle stops working while the bike remains running. When this happens, the yellow light on the instrument cluster comes on. I can cycle the key to get it to start working again. I changed the throttle assembly and it still happens at random. I read the threads on this site and didn't see anyone with a solution.

I don't see anything apparent in the wiring and wiggling the connections doesn't trigger the failure. The codes I get include "21F950 throttle grip sensor, comparing error..."

Anyone have and solve this issue?

Thanks
everything that @bennymx indicated is one of the solutions.

experience on my side is that my 2015 had a twist throttle replacement that I ordered from BMW dealer. I broke my original one at 625 miles. It fell on a trailer rail and tore crap out of the heated grip part. My replacement was put on by me, but the dealer sync the grip as at that time I was not doing any ISTA diagnostics yet. That twist grip seem to get out of sync, and my QS would quit working. Only a couple of times I had the !engine where the sync was out so bad it was the same as you describe. Whack the throttle and nothing happens. I replaced it with an ebay grip that was from a very low mile salvage bike, and now I had all the ISTA software and hardware. I was able to use it and resync myself on it. That grip never again got out of sync.

so you can try the reset adaptations and reset twist throttle position. you might have to replace the unit if it persists.
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post #4 of 9 (permalink) Old 05-21-2019, 08:46 AM Thread Starter
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Thanks for the replies.

I have changed the twist grip assembly with one from Alpha. The problem occurred prior to changing it out but the OEM throttle came apart, and although I put it together again, I figured it was malfunctioning and causing it to stop working, so replaced it with the Alpha.

I have recalibrated it a couple times. I inspected the wiring, especially the little plug that goes into the twist grip housing. It looks in fine order and when I wiggle the connector and the wires going into the connector it does not trigger the issue.

Because its so intermittent, I have no idea how to find the problem. It sucks because it fails on the track, and that can be quite dangerous.

Thanks for any input.
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post #5 of 9 (permalink) Old 05-21-2019, 10:41 AM
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I dont know who makes this magic Alpha unit. Most likely it is just a reworked OEM unit.

Heres the deal on how this thing works. There is 2 potentimeters inside the twist throttle assembly. It is called a comparative circuit in design. In the 10-14 there was just the TPS ( throttle position sensor ) on the throttle bodies, and we still had cables from the twist throttle to the TB's. Now, there is 2 TPS at the twist grip, 5 wires that talk to the ECU ( throttle by wire ) ( drive by wire ) . The first one sets up the voltage and is primary to the ECU, the 2nd one is in sync with the first and tells the ECU is is moving at approximately the same value. The error of difference is 2%. ( well it was in general motors APP ( accelerator petal position ) )

The problem with this design is that the carbon elements of the potentimeter can fail in resistance value at XX throttle position of the hand. So if TPS1 is at 3 volts and TPS2 is at 2.66 volts, this creates the error code and ECU shuts down receiving information and moves to default idle value so you can pull over.

If your twist grip from alpha continues to get out of sync with itself, return it. ( good luck dealing with George on that ) .. Does the alpha really have any advantage over the OEM unit? If you are leaning toward the old days of 1/4 twist turn response, what is going on there is that they are messing with the resistance values in increments. Not really very safe to that.
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Check out MotoMillion also has programming for RCK3 / HP power Kit enables now
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post #6 of 9 (permalink) Old 05-21-2019, 10:54 AM
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Maybe shift assist confusing ECU ?
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post #7 of 9 (permalink) Old 05-21-2019, 11:00 AM
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When it goes into limp mode, as in the grip is twisted and there is no engine response with RPM, there is usually a !ENGINE error on the cluster too.

You can turn the key off and back on ... sometimes this will reboot the ECU to resync with the twist grip and start working again.

When he indicates it stops working, I would be trying to figure out if it is at a certain twist value. Like it always occurs in turn 3 at 30% throttle. There is a resistance value for that and if Alpha is getting someone to rework the resistance values so it is a quicker turn response, I would be worried about how they implemented that.

Riding and loving my 2020 K67 with the custom XWORKS ECU
Check out MotoMillion ( forum Vendor section ) for all your needs in ECU work
Check out MotoMillion also has programming for RCK3 / HP power Kit enables now
Programmer for MotoMillion is myself ( BMW_388 )
I personally own the 2014, 2015, 2018, 2020 S1000RR
This makes for checking my ECU work is perfect every time sold by MotoMillion
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post #8 of 9 (permalink) Old 05-21-2019, 12:03 PM Thread Starter
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Great info, thanks for that.

I have not observed a connection to the throttle position and the failure. I can start the bike, and the error occurs immediately or not. I can be on the track and it happens while riding. I can't say I can tell. I can't seem to trigger the failure by moving the throttle. The thing is, the OEM was doing this too, which makes me question whether it is the Alpha part. The reason I went with Alpha was the durability (crash survivability) and the quick throttle.
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post #9 of 9 (permalink) Old 05-21-2019, 12:10 PM
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Great info, thanks for that.

I have not observed a connection to the throttle position and the failure. I can start the bike, and the error occurs immediately or not. I can be on the track and it happens while riding. I can't say I can tell. I can't seem to trigger the failure by moving the throttle. The thing is, the OEM was doing this too, which makes me question whether it is the Alpha part. The reason I went with Alpha was the durability (crash survivability) and the quick throttle.
august 2015 there was a bad update to the ECU ... later in December 2015 there was a new update that needed to be applied to those that were having twist throttle issues.

maybe you need to seek a dealer for an update on the ECU.
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Riding and loving my 2020 K67 with the custom XWORKS ECU
Check out MotoMillion ( forum Vendor section ) for all your needs in ECU work
Check out MotoMillion also has programming for RCK3 / HP power Kit enables now
Programmer for MotoMillion is myself ( BMW_388 )
I personally own the 2014, 2015, 2018, 2020 S1000RR
This makes for checking my ECU work is perfect every time sold by MotoMillion
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