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Discussion Starter #1 (Edited)
Post refers to a failing throttle control unit on my Monster 821... trouble shooting, symptoms and solutions.

First off; I can't say with any certainty as to what happened exactly to cause it to fail initially... after 36k miles the wires are heavily oxidized which leads me to believe this part will be doomed for failure. . . repeatedly. . . the first occurrence was right after my first valve service; which I did myself. I don't know if I had disconnected the cable for the throttle or if I otherwise stressed the attached wires but within 5 miles after completing the service I was calling for a tow truck fearing the worst...Que "ENG ERR" #1. Once it was towed home I set out taking it apart and putting it back together... I was looking for something I had missed... found nothing but that "simple" act lasted 5,000 miles when it kicked into Nanny mode and eventually locked the engine down in the your not going anywhere mode...towed to dealer this time where it sat for 6 weeks...no permanent solution...other than I was told it was a loose wire. Periodically I would get thrown into nanny mode; I would shut it down and restart it, which usually reset the fault...shutting it down and restarting seemed to work over the next 10,000 miles but with increasing frequency... I could go 2,000 miles without a problem ...then ENG ERR... 1,000...then 500...then it became a matter of feet...it wasn't until the error persisted and wouldn't reset that I was able to zero in on the faulty wire(s)... fortunately I was home.

So with the error not going away, I swapped in and out replacement parts looking to narrow it down...the {ENG ERR} fault specifically names 14 systems and I had swapped out all but the throttle control unit...so there it is I thought...doubting the assembly is broken because it works fine and especially because I have never tampered with it; I looked towards the clip...I could see the wires were clearly being stressed from the clutch cable underneath it...I fiddle with them and the error went away...I put a zip tie around the wires leading out of the frame so anytime the error would pop up I could just jostle the wires and be on my way...I got about 30 miles before it happened again and no amount of tugging would clear it...and in addition; I got stuck in a rider mode...its saying to "CLOSE GAS"....engine on or not...with the ENG ERR active or cleared it says CLOSE GAS...It went away after about 10 minutes of limping around...so now I'm sure I found the problem area, so I look at the other half of the clip...this one leads to the TCU and its a mess...with everything neat and tidy on the bike this one has its 8 wires just willy nilly coming out of the clip for a good 3 inches...I feel I'm staring at the problem so I remove the clip and could see that only 6 wires get used out of the 8...the wires are all pressed over in one direction putting much strain on the 2 on the end...the opposite end wires in the TCU clip aren't being used.

I reconnected the clip with the wires no longer being pushed to any side...they were all relaxed...no ERR...fixed? well...no. I did make it a few feet... pushed them back to their stressed position and headed home... RPM now limited to ~ 6000 rpm 87 mph top Speed... the connection was there but very weak...this time I removed the wires from the clip itself and was sure I would find a short...I couldn't find any short...I stripped back one of the wires and it was really really oxidized but it was still together...placing them as individual wires into their corresponding clip I pulled a few out to see what happens...when I tried to change rider mode CLOSE GAS immediately popped up ...putting it back in immediately didn't resolve the error...I still had to turn the key off and back on to reset the throttle position...and the only way to clear this type of ENG ERR is to turn the key off and back on...apparently the throttle position sensor is reset at key on and is lost if the clip is undone...so rather than do nothing this time; I cut the wire with the most severe kink and spliced in one of the unused two...put the clip back together and so far so good... 750 miles error free thus far

In the end; I found no short in any of the wires...I pulled hard enough to break a slightly broken wire and nothing happened...the wire I cut out was very oxidized but it was also intact, no breaks ...so this has me thinking its more of the connection within the clip itself rather than any kink or short in any of the wires? I swapped out the entire wire harness at one point and within 500 miles... you guessed it...ENG ERR. . . So I can rule out the lower clip..having bent some of the pins accidentally during disassembly they maybe making fresh contacts...time will tell...I have ordered its replacement already but I feel this is likely the fix. I'm leaving it in play and if happens again I'm gutting it for more answers....again
 

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Discussion Starter #2
the fix I described in the previous post did work...it lasted for 1k miles and then one day I left it out in the rain and it tripped the CEL the next morning...I already had the replacement on hand so I swapped it out...and it was like night and day on the power that the bike was now making...how I missed pulling wheelies in 3rd out of corners is a mystery...but first some diagnostic criteria to help isolate the TPS from anything else when the CEL comes on.

CEL: don't shut it off, try and change engine modes-NO..TPS...its that simple.

turn it off and the CEL resets, now try changing engine modes-YES...the TPS is not totally gone...yet...try full throttle...riding or stationary...did you make it to red line? when mine was at its worst I could not get above 6k rpm before the red line lights on the dash lit up (This is not limp mode) I was held at 87mph as a result...(if you suspect your TPS and have the road...go for a full throttle run...I never was able to top 119 since I worked up the nerve to go for it)

Every time I messed with the cables to the TPS things got better but were never fixed...pinning it coming out of a corner could immediately shut the engine down...on the highway in the fast lane in traffic slowing to 40 without brake lights was terrifying...if your experiencing symptoms this is the sort of thing that is coming your way.

its been 4k miles and things are going good...I am under no illusion that this is fixed... after dissecting the original I can say this is going to happen multiple times in the bikes future...wires corroding under their coating is never a good sign and explained why the signal was diminishing...

 

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Thanks for this, it is happening with my 2015 M821 now as well. I took apart the connector and cleaned it with contact cleaner which seemed to work for a while but just now it reappeared after 1K miles.

The only fix is a replacement APS I assume.
 

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Ducati Monster 821 APS strip down

I have taken the APS off to strip it down further to see if I could see anything internally. Please see photographs.

There was a build up of grease, I have cleaned this off now and replaced it with a spritz of Servisol Super 10. I have also cleaned the contacts again with WD-40 contact cleaner and completely unkinked the cable.

I will post again if this improved the situation any.
 

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Discussion Starter #5 (Edited)
I have taken the APS off to strip it down further to see if I could see anything internally. Please see photographs.



There was a build up of grease, I have cleaned this off now and replaced it with a spritz of Servisol Super 10. I have also cleaned the contacts again with WD-40 contact cleaner and completely unkinked the cable.



I will post again if this improved the situation any.
Stop...save yourself the headaches that are coming and just replace it...any modification you do will be short lived...I'm thinking that the person assembling it initially used the wrong flux or the wrong cleaner...the best solution is to replace it outright...save the throttle tube and use it for a set of heated grips...I chased this flaw for nearly 18k miles and was a miserable experience...I haven't had 1 issue with the new unit....it's money well spent

61,500 miles and counting

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Yeah you're right, the problem will be sealed within the epoxy somewhere and completely unserviceable. Just took it out and it still feels weak somehow. I see a replacement APS has a different part number from 2014 > 2015 (pictured) so there must be a known problem with the 2014 APS units I assume.

It's encouraging your monster still going strong at 61K however.
 

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I have the same issue with error code and limp mode 2-3 times in the first 13k miles, then one day it just happen on every ride and it was miserable... Saw this post and also found others on the internet that this is quite common issue with the first gen, replaced throttle units and haven't had issue in the last 1000 miles since it's swapped, power delivery also felt different as well.


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Discussion Starter #9
Did you notice an increase in power? I can't power wheelie even in 1st?
The longer you keep the failing unit in use the more the power is taken from you...as to power wheelies...it's all about RPM range and timing...the 821 won't do a tailstand wheelie in first but it will float the front end coming out of a corner up to third gear if your aggressive enough

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Hi Buhgaboo

Just to finish this thread off I recently had a big service carried out at Ducati. They plugged it in to the DDS and whilst they couldn't say for sure it was the APS the attached read out suggests the most recent check engine lights have been related to a faulty APS.

I have ordered a new APS, do you know if I have to get the TPS reset after I install the new APS, if not it'll save me a trip back to Ducati.

Best

M821 AWK
 

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Discussion Starter #11
Hi Buhgaboo



Just to finish this thread off I recently had a big service carried out at Ducati. They plugged it in to the DDS and whilst they couldn't say for sure it was the APS the attached read out suggests the most recent check engine lights have been related to a faulty APS.



I have ordered a new APS, do you know if I have to get the TPS reset after I install the new APS, if not it'll save me a trip back to Ducati.



Best



M821 AWK
Plug it in... ride on...tps resets everytime the key is turned on...

you will need a need a security t-25 torx bit to remove/install...vroom vroom

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I have the same problem with my 2018 Ducati monster. I see the message “close throttle” on my dash and I can’t change riding mode. Also have a check engine light came on. After reading you guys I replaced the throttle control unit. I turn the key on without turn on the engine the problem still there. Do I have to bring to the dealer to reset or anything? please help.
 

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Discussion Starter #13
I have the same problem with my 2018 Ducati monster. I see the message “close throttle” on my dash and I can’t change riding mode. Also have a check engine light came on. After reading you guys I replaced the throttle control unit. I turn the key on without turn on the engine the problem still there. Do I have to bring to the dealer to reset or anything? please help.
The check engine light will go off with the engine running....and it always stays lit for a second or two on startup...the throttle resets itself every time the key is turned on...no dealer help needed
 

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Thank you everyone. My problem is solved. I turned the engine on and went out to ride for about a mile and got home. I turned the key off then on then the light went away and I was able to change the riding mode again.
 
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