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cam sensor question

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Old Aug 5th, 2013, 10:39 PM     #1
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cam sensor question

I am a new member. I would just like to bounce some info off you for a second opinion. I am working on a friends 98 FLHTCUi because of a stalling issue. The stalling occurs in any gear, any speed and will occur as soon as 5 minutes after start up. The bike stalls, no bucking or hesitation....just quits. About two to three seconds before it stalls, the check engine light comes on.

During these few seconds, the bike can accelerate normally or cruise without a problem. The engine then just shuts down. To get it started, all I have to do is cycle the ignition or kill switch. I am so used to doing this that I cycle the switch while riding and dont even use the starter unless it stalls at low speed. The check engine light does not stay on after it starts up again.

It has stalled up to 15 times on the hwy in less than one mile. Pretty scary when passing someone. I have also ridden for 2 hours without incident.

The bike has been to the local dealer and because of its updated computer (previous owner), they can't access scan data or any codes. The sticker on the computer says the data link is no longer operational. Even thou this is a HD computer, the dealer does not have the cable or software needed. Go figure.

According to the manual the VAS (vehicle attitude sensor) which is built into the cam sensor will shut the ignition down if the bike tilts below 80 deg. The only way to restart it is to bring the bike upright and cycle the ign or kill switch.
I'm pretty certain this is the area of fault but I'm not 100% sure.

These sensors are over $250 from hd so I'm wondering if anyone else has run across this problem. Also, is it possible to install a sensor without the VAS? I have checked all grounds and connections. I have swapped relays and updated the circuit breaker. The ignition switch and kill switch have been checked
I should also mention that just prior to stalling the tach drops to 0. Sorry for the long post. Thanks......your thoughts?
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Old Aug 5th, 2013, 10:44 PM     #2
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Re: cam sensor question

Not a long post at all. The more info available the better the help from the tech gurus here. So I am sure someone will be along to assist you soon....
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Old Aug 6th, 2013, 09:31 AM     #3
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Re: cam sensor question

It may not be the computer at all. Just after I rebuilt my bike I took it on a 3700 mile trip and would be riding along and all of a sudden the bike would quit with no warning all gauges to zero. I would coast to the side of the road and it would start again, sort of sounds like what you have.

The problem was I was missing the star washer from under the nut holding the positive battery cable to the starter. It had loosened up just enough that sometimes it would loose contact and the bike would shut down then when the vibration stopped make contact again and the bike would run. I was checked all the switches, computer etc. then found the cable not tight and the star washer missing (I must have forgotten to install it)

I installed a star washer, torqued the fitting and have not had the problem again. It may be something as simple as that.
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Old Aug 6th, 2013, 09:44 AM     #4
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Re: cam sensor question

Pull the sensor, clean it off and see what happens. I'm thinking a bad cam sensor would cause misfiring and not complete shut down. I'm thinking a bad VAS would just stop power to coil.
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Old Aug 6th, 2013, 10:18 AM     #5
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Re: cam sensor question

Quote: Originally Posted by tech2 View Post
friends 98 FLHTCUi .....the dealer can't access scan data or any codes..... The sticker on the computer says the data link is no longer operational. ............
I'm pretty certain this is the area of fault but I'm not 100% sure. Also, is it possible to install a sensor without the VAS?

If the cam sensor truly does contain a bank angle sensor and the sensor only has 3 wires coming out of it, I see no way to disable only the attitude portion of the switch. You could install a cam sensor that doesn't have a built in BAS, but it may come around to bite you down the road. On my own bike, ya maybe. On someone else bike,, probably not a good idea.

But what you could do is parallel a LED lamp to the output of the cam sensor that would flash in unison with the ignition firing. Duck tape the LED to the bars in plan view. Now when the engine did die, as long as the engine was still in gear and turning, the LED should be flashing on & off as you come to a stop.
If the cam sensor is the cause for your problem, the LED will stop flashing as soon as the engine dies. (even though it's still in gear and turning coming to a stop, you won't see any flashing)

If your near sure it is the attitude sensor, this would be a cheap way to confirm and test it. You first will need to take a meter and determine if the cam sensor is a "pull up" or "pull down" sensor. Then measure the reference voltage to see if it is +5 or +12. Once you know those answers, it is an easy hook up.

I sure would like to know more about this HD injected ECM that will no longer talk to a HD tech scanner because the previous owner updated it. Someone other than HD upgraded it and it has no aftermarket add on black boxes?.....but it does have a label on it that says it no longer will commo with a HD scanner.
Humm...
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Old Aug 6th, 2013, 11:51 AM     #6
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Re: cam sensor question

Thanks for the replies. I did verify the positive connection at the starter and all the grounds. I also tried using freon on the sensor and also a heat gun. I tried wiggling the harnesses, tapping on the sensor and it never stalled once. I like the idea of an led on the signal line....I'm going to try that and get back to you.
I tried to upload a pic of the ecm but I'm not sure if it will work. If not I'll try again later.
I did a little research on the VAS and it seems that the switch is in series with the ground wire of the hall effect in the cam sensor. Unfortunately it is just one tamper proofed sealed assy.
I will respond after I install the led and go for another ride. Thanks again.cam sensor question-ecm.jpg
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Old Aug 6th, 2013, 12:24 PM     #7
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Re: cam sensor question

Wow very interesting. It's almost like that ECM was some kind of Tool used by the dealership. It sure does look legit to me. Maybe it recorded data while you rode the bike and then you did a dump to a PC.??

They installed it on the owners to ride with and collect data. Then the guy just never went back to the dealership.
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Old Aug 6th, 2013, 02:26 PM     #8
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Re: cam sensor question

Quote: Originally Posted by wrenchin View Post
That ECM pictured is a blank service replacement installed by a dealer and programmed to the bike.
Strange it would say "data link no longer available...."
Once you change the ECM, you can't read codes anymore. I don't know enough about Magneti Marelli systems to know why that would be so.
I know it's not the case with Delphi because if it was, I would throw my bike away.
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Old Aug 7th, 2013, 12:33 AM     #9
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Re: cam sensor question

I had some time tonight so I hooked up two led's in parallel to the cam sensor. There are two 5v wires and one gound wire. The one 5v is constant and powers the hall effect switch. I put a green led on that wire and it stays on steady with key on and also when running. The other 5v source I put a red led and this is the signal wire. Depending on the rest position of the hall effect rotor, this led may stay on steady or be off (key on, not running). When running, the red led flashes on and off quickly and the green led stays on steady.

I will road test tomorrow and hopefully the stalling will continue. I will keep you posted.
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Old Aug 7th, 2013, 09:53 AM     #10
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Re: cam sensor question

Quote: Originally Posted by tech2 View Post
Depending on the rest position of the hall effect rotor, this led may stay on steady or be off (key on, not running). When running, the red led flashes on and off quickly and the green led stays on steady.

I will road test tomorrow and hopefully the stalling will continue. I will keep you posted.
Man, your GOOD! It sounds like your LED's already had current limiting resistors with them.

Fantastic. This should tell you something about whats going on with the bike. I'm curious to see.
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