Hello, a newbie (again) on the forum. Years ago, I was here, lurked without logging in fairly often, but now... that was several email addresses ago etc etc... you know how that goes.

For anyone having p0373 and p0374 issues, which is something amiss with the crank position sensor, some little info. One has to do with the bias voltage the other with the pulse itself, but really its looking at the same "wire" in two different ways. You can get one, the other, or both codes appear when the sensor is iffy, in a death spiral, or totally shot.

First - be very careful when measuring the ohms across the connections. I don't see any specific warnings, but my a few live brain cells left from "lectrical ingineerin'" tell me ouch, you can kill one testing it. The wire gauge is approximately AWG-54, and for folks not familiar, that's about .0008 inches. Yes. Eight ten-thousandths of an inch, and that includes the Formvar or whatever they're using for insulation. White guy's head hair is .0025 inches or so, or... about three times thicker than the wire in that coil! Guitar pickup wire is generally about AWG-42 for those who know about such items.

A potent VOM (say, a Simpson 260 or other analog meter) could very well blow the coil while testing it. What to do? Knowing what I do now, I think I'd put a 10k resistor in series with the meter lead, and test the "difference" in ohms between 10k and whatever it reads. Good coils should be about 1k (1000) ohms or so. Mine was 460k - bad. Some guys report 1megohm or so too - also bad. Anything higher than 1k should be suspect. That would be a reading of 11k with the 10k resistor in series with the leads.

There's very little magic with the Crank Position Sensor. A strong permanent magnet, a ferrous "slug" or "pole piece" (or "collector" or "concentrator" as some call it), and a coil of wire. That's it.

Speaking of guitar pickups, it works EXACTLY like a Gibson P90 guitar pickup. Magnet on one end of the ferrous pole piece (in the sensor its a hollow steel tube). The magnet touches the pole piece and the magnetism is focused at the other end of the pole. The end of the sensor is fairly close (not sure just how close) to the flywheel. Ridges on the flywheel interrupt the magnetic field and pulses are created in the coil... and send to the ECU. In effect, the ridges are the guitar "string", the sensor is the "pickup" and the ECU is the amplifier (well not an amp... but it uses those pulses). The ECU also provides a steady DC voltage as what's called a "bias" or offset, mostly so the pulses are compatible with the ECU's circuitry.

Here's another little tip - the coil can fail all at once, or can go bad slowly... and when it does, other little things can appear to be the issue. That is, the coil can open and not short unto itself. Its dead. Or, the coil can (and does) short winding to winding, reducing the way the ECU is able to determine crank position. When it shorts winding to winding, might get lower than 1k readings, and reduced pulse output. Then, eventually, the coil will open and go bad. The coil appears to be bifilar wound, meaning more than one wire used as part of the coil. Can't say for sure since it was sort of destructive examination. I'm only mentioning that, since you can probably get higher than 1k readings too, maybe 2k or 5k and that would show one of the wires open, the other still intact.

You might think there was a bad Deutch connector, or water in it (my thought, on my 04 Wide Glide), or a bad wire, or bad connection at the ECU. Perhaps there was compound problems, since taking the connectors apart and rejoining them seemed to "fix" the problem for a while.

And finally (and my problem) when I pulled out the sensor pole piece (after carefully slicing off the end cap on the part that is closest to the flywheel), it was obvious what my problem was. Water. The pole was rusted.

The rust made me seriously consider things. Water getting down into the sensor from the wires? Maybe. But, the end of the pole's tube was also exposed to engine innards - oil, combustion blow-by, etc etc. And, the new Harley sensor is sealed at the engine side, not open. I'm thinking condensation from cold/heat cycling, blow-by gasses in the crankcase, all the air moving inside the engine as the pistons move... eventually a bit of moisture to collect in the sensor. Rust formed. The coil sat directly on the pole and... whoops, there goes the coil.

One other thing, and I don't have the part number, but that sensor is the same as used on some Volvo's, made by Bosch. Not unusual to see crossover. The Bosch sensor comes with a long cable (about 2.5 feet) and the Volvo plug on it. In an emergency, you can beg to see what the auto parts place has, and splice wires and or transplant a new Deutch connector and be all set.

Whew. That's been my last little adventure with the bike, 70,000 miles and no real issues other than that and an open fuel injector coil. Makes me long for magneto and carburetor... but I don't think that's gonna happen.

 

Firstly, nicely written post, coherent, digestible, descriptive; good job!

I remember seeing a video of John Fogerty playing a Les Paul (Gold Top) with P-90s, trapeze bridge, sounded so sweet! I've always wanted a LP with P-90's, they just scream blood and murder so sweetly

I've been sitting here putting 10 thumbs to a Strat so this is timely

Good post, thanks for taking the time

 

Hey thanks! That @#@!! sensor starting driving me nuts about there years ago. I'd undo the plug, reconnect, it would fire. Then, if I shut down after a short run, say... I went down the block to get gas, maybe 3/4 mile. No restart until I fiddled and fiddled (and probably it was cooling). That sort of thing has been reported in a few threads here. All during this time, I was having the occasional extra long crank-to-start scenario, and some backfire on crank up too. That should have been a strong indication of bad spark timing... I wasn't paying attention.

And finally one day, no start. Fiddled and fiddled, got two putt-putts and that was it.

And... btw.... you CAN flood a fuel injected Harley engine, if its getting no spark. Trick is - and I learned it here - is to crank "wide open throttle" and the ECU knows to shut off the injectors while cranking at WOT. Nice feature.

I don't recall it in the HD Electrical manual, but I've also read that the tach (if you got one) should show rpm while cranking if the sensor is reporting to the ECU (or ECM, whatever they call it). Saw you can take out the plugs and crank easy to monitor that. My tach was all over the place while cranking... another sign.

While the 100hz crank position is easily monitored, I think... there's more going on with the pulse train. Not sure though. I know the engine will fire closer to TDC on crankup for easier starting, then shift to whatever is in its map for idle (or other driving condition such as higher RPM, load, etc). That "suggests" only TDC (or other fixed point) need to be determined, since rpm is not important during crank up. OTOH, it is important during operation when timing is advanced variably. I'd like to think that the programming in the ECU can figure this out within two or three crank rotations on the fly, but others have suggested that there are multiple pulses that go on to determine rpm as its happening (within one crank rotation). I'm not sure which is the case, and seem to think that the HD manual says its the latter.

What does this all matter? Sort of academic, but I think you can miss a surprising number of pulses and the engine will continue to run, as long as the crank position sensor "checks in" within some (unknown) number of crank rotations.

Lord I yearn for a magneto and carburetor again.... life used to be simple.

 

And I ought to say.... I never wound my own pickups, but got P90's on an SG, LP and Tele (latter two in the neck position). Sort sound like the perfect marriage of a Strat pickup on steriods and HB fullness. Thanks again!