Error Code C28

[Proteous]

Hi Guys..

Some assistance needed.. I'm getting error code C28 and the engine is revving its twat off when I first start then the revs drop and the FI light flicks up. The Error points to secondary throttle valve actuator (STVA) but that appears to be functional and doing its job. It does the ignition on sweep as it should so I'm at a bit of a loss.. TPS SEEMS ok and the valves are all synced as they should be..

Any ideas?

[Proteous]

Update.. I think it may be the STP sensor.. the ohms it should be reading in the manual isn't even close.. should be 800 closed and about 3.9 open.. but I'm getting 270 to 310.. barely moving.. hmmmm  guess I'm posting in the sales and wants section.

[Blubber]

Sounds like you found the source of your FI light blinking   

I get the confusion since a faulty STPS should be error code C29, not the C28 you get.

Based on your reading on the STPS it's almost dead and therefore needs replacement.

You'll need part 16 - part no 13580-42F00.

or... you can get a complete used set of body's on ebay incl the TPS, STVA and STPS - money wise almost the same.

[Proteous]

Yep, thats what i recon.. this is the problem with errors such as these error 28 is secondary throttle valve actuator but it only thinks that because its not getting the correct reading from the sensor further down the line.. so it took about an hour to trace where the actual fault was.. I say 'I' in all this, but its more 'my mate' lol

Anyway, off to the wanted section i go to see if anyone has what i need.

[seth]

sorry i cant help jay but have you checked Robinsons for part numbers to see if same part fits other bikes
surely gsxr 1000 or 1250 bandit might be the same and lots more sold so more choice

good luck buddy

[Snapey]

I know I harp on this but magnets in the STVA can come loose thus stopping proper operation. A simple test is to reach under the throttle bodies & make sure the choke shaft pivots freely before looking for sensor problems.

[Proteous]

I know I harp on this but magnets in the STVA can come loose thus stopping proper operation. A simple test is to reach under the throttle bodies & make sure the choke shaft pivots freely before looking for sensor problems.

Checked over ALL moveing parts bud. All move freely.. The most irritating part is that the ignition sweep work flawlessly. So the error code didnt make any sense.. The actuator itself is working but the sensor just isnt readint the open position so it throws up massive revs. then the ecu says oi, thats not right and shuts it off throwing up the C28 error..

Thats what we figured anyway.. I am suprised however that noone else has suffered this.

[Snapey]

Lost me then ... good luck with your search.

[alfadave]

curious but what work have you done recently on bike in throttle body area ? have you had them off?

[bigian14]

I know I harp on this but magnets in the STVA can come loose thus stopping proper operation. A simple test is to reach under the throttle bodies & make sure the choke shaft pivots freely before looking for sensor problems.

Checked over ALL moveing parts bud. All move freely.. The most irritating part is that the ignition sweep work flawlessly. So the error code didnt make any sense.. The actuator itself is working but the sensor just isnt readint the open position so it throws up massive revs. then the ecu says oi, thats not right and shuts it off throwing up the C28 error..

Thats what we figured anyway.. I am suprised however that noone else has suffered this.

I too have just suffered the same C28 error code and have been following this thread with interest.
Doesn't seem to make any difference to how the bike starts or runs and as has previously been mentioned I have checked for free movement of the choke shaft.
I'll check the STP sensor when I get time but in the meantime I have purchased a used set of K7 bodies complete with all sensors etc, for what appears to be sensible money, (£169 against over a grand new!), bearing in mind sensors are best part of £100 or more depending on which one is needed.
Question is, do I replace the whole assembly or just the part/parts I may need?
For the record, I am now running individual pod filters but doubt that caused the error as nobody else with pods seems to have encountered the same problem and this isn't the first run out since fitting them.

[seth]

if they off a running bike
fit complete and then balance the throttle bodies
you can then swop your buts over till it fails then you find the problem.
other wise you might chase your self for long enough

good luck

[KiwiCol]

Nice way to find the error Seth, very good! 

[gsxbarmy]

I know I harp on this but magnets in the STVA can come loose thus stopping proper operation. A simple test is to reach under the throttle bodies & make sure the choke shaft pivots freely before looking for sensor problems.

Checked over ALL moveing parts bud. All move freely.. The most irritating part is that the ignition sweep work flawlessly. So the error code didnt make any sense.. The actuator itself is working but the sensor just isnt readint the open position so it throws up massive revs. then the ecu says oi, thats not right and shuts it off throwing up the C28 error..

Thats what we figured anyway.. I am suprised however that noone else has suffered this.

I too have just suffered the same C28 error code and have been following this thread with interest.
Doesn't seem to make any difference to how the bike starts or runs and as has previously been mentioned I have checked for free movement of the choke shaft.
I'll check the STP sensor when I get time but in the meantime I have purchased a used set of K7 bodies complete with all sensors etc, for what appears to be sensible money, (£169 against over a grand new!), bearing in mind sensors are best part of £100 or more depending on which one is needed.
Question is, do I replace the whole assembly or just the part/parts I may need?
For the record, I am now running individual pod filters but doubt that caused the error as nobody else with pods seems to have encountered the same problem and this isn't the first run out since fitting them.

I vaguely recall that there are some minor differences between the earlier model throttle bodies and the later ones - no idea what they are, Snapey pointed it out - but on the old org, and he now can't recall quite what the differences were as it was some time ago. Whether in practice they make any difference to the running of the bike - no idea.

Suppose try and test and see what happens - why not

EDIT: Here's where I read it - see the 5th thread down.

[bigian14]

K1 bodies different, (not sure in what way), K2 to K7 listed as exact same part number with Robinsons Foundry as are all the ancillary components.
If I find it is the STP sensor I may just change that over or maybe even fit a new one and keep K7 throttle bodies as spare or move them on.
I'll let you know how it goes, they're being delivered tomorrow but realistically won't have time to work on bike until Friday at the earliest, possibly Thursday night.

[alfadave]

I have seen this error on a bike I had to diagnose ....the owner took off the secondary sensor ,cleaned it out and lubed it again ....then refitted it .then he got the code issue not long after ....when I looked at it I noticed that the sensor was putting pressure along the spindle ...because the ecu actuates the motor ,it also monitors the energy used to activate it ...and I tell you that it doesn't take much for it to throw a code.....so if your spindles in secondary are not in sync that can cause a resistance as well when they are actuated in normal running
as for throttle body synchronising this will only help response down below and make engine smoother ....tps set at 1.1k (this has to be accurate)with tickover  set at 1200 rpm ....the secondary sensor and the tps  inconjuction with each other should amount to a certain voltage  ..its in the manual ,cant remember ...
also a very high idle starting can be down to a bent arm on the fast idle actuator so check that ,it doesn't take much 
ps difference between throttle bodies is the fuel rail ones alloy ,tother is metal I believe