04 SXVIPER DCS light again.........

H

holm0069

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Jan 26, 2013
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45
Location
Ottawa, Ontario
Having issues with my 04 Viper. Posted here last year and have not made any progress. Only has 700km on it.......looks and runs new. At around 7-8k RPM dcs light flashes slow then begins to flash faster if I continue to hold the throttle (which I don't do for very long, just trying to diagnose). Has been in and out of two reputable Yamaha dealers four times now and they have little info for me. Put 160 main jets in and raised the needles as per info that was given to me by someone else. Valves, carbs, everything has been cleaned. I run high grade fuel as well as octane boost but makes no difference. Haven't been able to ride this thing since I bought it because of light...................its been almost two years. Dealer thinks next step would be to put a thicker head gasket in it or change the sensor (which he has never had to do before). I'm lost.....

If someone could diagnose this problem for me words would not describe how grateful I would be. My friends all ride around and have a great time together and I'm nothing but a loser sitting at home with a sled I can't drive........a big dumb loser.

Please help.
 

It could sounds stupid but what kind of clutch set up do u run? u must know that agrresive clutch set up create alot more heat in the engine
 
is the sled all stock?

or does it have a exhaust can, aftermarket clutching,cold air kit, gutted airbox, any add on's?
 
ok, then since everything is stock lets do a little test.

Do you have anywhere around you where you can buy 1 or 2 gallons of race fuel from someone who drag races or even airplane 100low lead?
 
Try searching "TPS performance issues" for a post from Sideshow Bob. It was specific to a 2002 SRX and by 2004 the TPS may have been updated but it's worth the read. If nothing else you could check the part number Bob provides in his post to see if your TPS may be suspect.
 
drain the sled down to half a tank, then add 2 gallons of race juice and go test it out, report back.
 
I had a 04 MT viper that I piped and put an aftermarket head on. Sold the sled before I ever even got it together....came back to me 3 times with DCS issues. Tried everything to no avail then he ended up with a coolant leak and blew the motor. It's back in my garage right now getting a rebuild and going back to stock. I hope that's the end of the DCS nightmare....this sled has been a thorn in my side.
 
I've researched alot on the dcs on my srx. It seems like these things trigger it:

-octane too low, try gas from different stations.
-jetting too low
-motor heats up after a long run, setting it off.
-coolant too warm, usually gets it going after 70 celcius or above
-too aggressive of a clutch set up.
-powervalve(s) not working properly, look for a pull through
-tps out of whack
-too sensitive of a sensor
-gearing too tall, lugs motor, much like the clutch set up.
-exhaust leakage, check if doughnuts between pipes are good and the springs are tight.

other things may also cause this:
-head modification
-wrong sparkplugs.

From what I've seen, pipes don't work with dcs on a viper. It will triggger it all the time.
 
Will only that knock sensor set off the DCS light?

Thanks for all the info to by the way for everyone that has offered some.
 
holm0069 said:
Will only that knock sensor set off the DCS light?

Thanks for all the info to by the way for everyone that has offered some.
Click to expand...

The knock sensor detects detonation (spark knock/rattle) and sends a voltage signal to the CDI which will reduce the spark advance. It's the same technology as the spark igniter on your gas grill. You excite it (pushing the button) and it produces voltage. It is "tuned" to produce a voltage when it's excited by the vibrations produced when two flame fronts collide within the cylinder.

As Norwegian suggested, there are many causes for spark knock and as Mr. Viper suggested, start with changing your fuel to ensure it isn't a contributor.

To answer your question - the knock sensor is only the messenger and probably doing it's job.
 
the knock sensor doesnt create voltage like a gas grill ignitor, it has voltage all the time from the cdi circuit, its more of a "microphone". If the detonation occurs the sound pulses go thru the coolant and it interupts the standard or cdi read normal range/voltage signal and the cdi senses the voltage differance or "out of frame" and it goes into its ign. timing retard cycles, as it continues it goes farther into retard from the knock sensors listening to the pulse waves in the coolant. Then from continuing detonation, it will then go to just a limp home mode(reduced engine power).

you would need a occiliscope to see the voltage waves from the sensor. voltmeter wont read that fine of voltage.

but to answer the original posters question, yes its just the sensor on the head that does the dcs.
 
When trouble shooting my SRX DCS issues I found that the DCS warning was never a false warning. Something was going on with the engine that the DCS sensor was accurately detecting.
I tried different sensors and CDI boxes with the same results.

As you have already been advised, I would start with known high octane race gas and see if the DCS quits flashing...start with the simple stuff.
 
mrviper700 said:
snip

Perhaps sled mfgs. use different technology to detect spark knock. Given that they use the same automotive technology to monitor throttle opening, baro, a/f ratios (UHEGO) and even fuel level, I assume they use the technology the automotive world has used for 30+ years to detect spark knock. Perhaps my assumptions are incorrect.

My previous post was a bit simplistic, but a typical knock sensor is a piezoelectric device that uses quartz crystal technology that produces a voltage when excited/vibrated just like your gas grill igniter but in a slightly different way.

The reference/offset voltage sent to the knock sensor is used so that the voltage output spikes generated by the knock sensor are independent from the normal spikes that occur in the system (headlight, warmers, ignition coils, etc.). The amplitude and duration of the voltage spikes the sensor produces dictate the amount of spark advance pulled. The circuitry is typically shielded to avoid RF interference. Unlike a thermistor or other varying resistance type sensors, a knock sensor produces its own electrostatic voltage… when excited.

It is true that the knock sensor is sort of like a microphone and it is also true that for some diagnostic purposes an oscilloscope is used to monitor its output, but to suggest that a knock sensor does not produce a voltage in incorrect.

I’d be interested to see what is used and will defer to your expertise if piezoelectric isn’t used. Otherwise, I stand by this and my previous post.
Click to expand...
 
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