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ECU code 21?!?!?!?!

arcticcatwill

Active member
Lifetime Membership
Nov 26, 2007
410
32
28
Lewiston, id
2010 m8. So I replace my knock sensor and its still throws the code. I run non E premium fuel only. Basically when it has the code active it acts like it has a rev limiter at 7800rpm. I have a polaris primary clutch with 66g weights. My buddy said his 11' m8 did the same thing when he over rev'd the motor, a sort a limp mode. Said he added weight and it quit doing it. but he couldn't remember what code he had. before i buy weights i thought id post on here.

Any input would be awesome.
 
M
Oct 4, 2015
538
147
43
Montana
ECU code 21

Can't remember where to look up ECU codes, but google it, & I am sure you will find it. With that being said, it is probably a low octane sensor code. Back in 2012 Cat sent out a customer bulletin to have the ECU reflashed by dealers to fix the problem; I got one (bulletin) for my '11 CF 800. Since I was not seeing trouble codes on neither my '10 M8 nor my '11 CF 800,my dealer wisely suggested not to do the update. I am very glad that I did not do the re-flash (? non-revereseable?) I only run non-E 91 octane fuel & if there is any question re: octane, I will add a bit of AV 100 LL from the airport; AV fuel won't make a stock 2-stroke run higher HP, but it will not hurt it either. The AC re-flash pulled back the timing advance to eliminate the detonation & the ECU code. That is also one reason why the '10 & '11 800 Suzuki engines made 8 to 10 more HP than the '12 & up Suzuki 800;s! Try to find a way to increase/insure your octane @ 91 & see if the code does not return after re-setting the module. My 2 cents worth.
 
S
Aug 28, 2017
49
9
8
oregon
Watching this thread....my 11' m8 doing the same thing. I only use non-ethanol. Dealer said it coded 19x for faulty knock sensor. Ordered one beginning of mo. & it's still not here. My pipe support bracket above belt was loose also & spring was barely tight. Fixed both and still coded last weekend. Keep us posted.
 
M
Mar 18, 2011
360
54
28
48
Manitoba
Knock is ecu21, check for anything that could send vibes . Even rail end caps, 11s had bumped timing over 10s I believe. Try 2deg key backwards
 
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