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2009 prostar isx crankshaft sensor issue - Zmcd - 01-01-2025
2009 prostar isx 450hp
Thanks for letting me join first of all.. I was having issues with my truck losing power randomly. Had a code for cam sensor so swapped it out. Truck ran smooth for half the day. Then had bad random loss of power with the rpm’s fluctuating from normal to dropping really low. Had a crankshaft sensor code. I tried to remove the sensor but it broke trying to take it off. I took it to a mechanic and they drilled the sensor out and replaced it. I’m just finding out they drilled thru some of the teeth on the tone ring. Now I’m having the same issue. I swapped out ecm and engine harness not knowing that they had drilled thru the tone ring. They state it isn’t an issue, but I’m thinking this is the problem on why the truck continues to read that error and act the same. Does that sound right? I apologize if I sound foolish, just need to get this truck running it’s been down a month.
RE: 2009 prostar isx crankshaft sensor issue - DVT873 - 01-01-2025
Not an issue!?!! If the tone ring is missing teeth it will sure as hell cause problems. If there was rust or corrosion under the sensor tab and they didn't clean it up that will cause problems also. Like rust-jacking on brake shoes it pushes up on the sensor forcing the tip of the sensor away from the tone ring. On mid-range Nav engines, the maximum clearance is .070. Beyond that, the signal starts going to hell, to the point it won't start. I don't know what it is for Cummins but I would expect it to be a similar clearance.
If you can find somebody who can use an oscilloscope they can look at your sensor signal. Dam few truck mechanics will know how to do that but a good hotshot automotive guy will. They scope cam and crank sensors a lot.
RE: 2009 prostar isx crankshaft sensor issue - Zmcd - 01-01-2025
(01-01-2025 )DVT873 Wrote: Not an issue!?!! If the tone ring is missing teeth it will sure as hell cause problems. If there was rust or corrosion under the sensor tab and they didn't clean it up that will cause problems also. Like rust-jacking on brake shoes it pushes up on the sensor forcing the tip of the sensor away from the tone ring. On mid-range Nav engines, the maximum clearance is .070. Beyond that, the signal starts going to hell, to the point it won't start. I don't know what it is for Cummins but I would expect it to be a similar clearance.
If you can find somebody who can use an oscilloscope they can look at your sensor signal. Dam few truck mechanics will know how to do that but a good hotshot automotive guy will. They scope cam and crank sensors a lot.
It’s definitely drilled thru, looks like teeth were drilled thru on the corners and the edges were chipped off. Gonna have to look into swapping the tone ring.
RE: 2009 prostar isx crankshaft sensor issue - Rawze - 01-02-2025
(01-01-2025 )Zmcd Wrote: ...
It’s definitely drilled thru, looks like teeth were drilled thru on the corners and the edges were chipped off. Gonna have to look into swapping the tone ring.
yeah... damage to the tone ring causes false/unstable signals.
Whatever complete idiot, that drilled it out, without dropping the pan and protecting the tone ring should be contributing towards the tone rings replacement.... which is NOT going to be easy to do by any means.
RE: 2009 prostar isx crankshaft sensor issue - Zmcd - 01-02-2025
(01-02-2025 )Rawze Wrote:(01-01-2025 )Zmcd Wrote: ...
It’s definitely drilled thru, looks like teeth were drilled thru on the corners and the edges were chipped off. Gonna have to look into swapping the tone ring.
yeah... damage to the tone ring causes false/unstable signals.
Whatever complete idiot, that drilled it out, without dropping the pan and protecting the tone ring should be contributing towards the tone rings replacement.... which is NOT going to be easy to do by any means.
And that’s exactly why I’m still getting erratic rpm readings and bad crankshaft code. I’m going to go to their shop today and figure this out. I hope I can be back up and running soon. Thank you all for the clarification. Will driving it like this effect my ecm? Gotta get the truck to their shop
RE: 2009 prostar isx crankshaft sensor issue - Zmcd - 01-02-2025
(01-02-2025 )Rawze Wrote:(01-01-2025 )Zmcd Wrote: ...
It’s definitely drilled thru, looks like teeth were drilled thru on the corners and the edges were chipped off. Gonna have to look into swapping the tone ring.
yeah... damage to the tone ring causes false/unstable signals.
Whatever complete idiot, that drilled it out, without dropping the pan and protecting the tone ring should be contributing towards the tone rings replacement.... which is NOT going to be easy to do by any means.
Would this fault still happen while I’m idling? I just got to my truck, and before on the old ecm and harness the truck would have erratic rpm’s if I stepped on the pedal over 15k rpms that’s where the truck would start to have erratic rpms. Right now it is no longer doing that, after swapping ecm and engine harness. I can step on the pedal and keep on it without the truck having any issues, however I have yet to try it on the road.
RE: 2009 prostar isx crankshaft sensor issue - Notch - 01-03-2025
Until you replace the damaged tone ring you won't be able to troubleshoot this properly, even though the issue is **almost** guaranteed to stem from the crankshaft tone wheel at this point.
The reason being, the ECM references crankshaft position (aka where #1 piston top dead center is/was/going to be) based on a number of teeth on the tone ring as it passes the sensor. If you just have a bunch of teeth on the wheel then you will never know if the piston is up or down, just that it's moving. So to reference position of the crankshaft/piston, the engine makers leave a tooth off the wheel and the computer is able to count the teeth in between this "blank space". So if someone gives the tone wheel a new "blank" space then the ECM has no way to know if this space is supposed to be there or not, or if the piston is actually up, down, or where it is for calculation of engine speed, cylinder identification, etc.
Looking through my waveform library I found an old reference pattern screenshot from a CM871 BAC that I screenshot and saved for a know good reference. This is just a line pattern of voltage of a crankshaft position sensor output with an engine running at idle. There are 2 wider spaces in this waveform indicating the "missing tooth" space on the tone wheel. If you were to count the "mountain peaks" between the 2 wide spaces they would equal the number of teeth that are on a crankshaft tone wheel. If you were to knock another tooth off, the ECM wouldn't know any different and would think that the blank space was the factory reference missing tooth and not the one drilled off, throwing off all sorts of injection timing events.
Replace the tone wheel and report back.
RE: 2009 prostar isx crankshaft sensor issue - Zmcd - 01-03-2025
My truck has been at a shop for 5 weeks now. A different shop, not the one that drilled the crank sensor out. After replacing the ecm, and engine harness the issue is gone. The truck runs normal as far as the motor goes. It runs smooth without erratic rpm changes. I’m now having a different issue I will make another post for. I know for a fact the tone ring is damaged, I saw where it got drilled thru. Teeth are still there, just damaged or chipped at one corner. But truck seems to be running good now.
RE: 2009 prostar isx crankshaft sensor issue - Notch - 01-03-2025
(01-03-2025 )Zmcd Wrote: My truck has been at a shop for 5 weeks now. A different shop, not the one that drilled the crank sensor out. After replacing the ecm, and engine harness the issue is gone. The truck runs normal as far as the motor goes. It runs smooth without erratic rpm changes. I’m now having a different issue I will make another post for. I know for a fact the tone ring is damaged, I saw where it got drilled thru. Teeth are still there, just damaged or chipped at one corner. But truck seems to be running good now.
It sounds like there is probably enough of the tooth left on the damaged one/s that the crankshaft position sensor is still able to pick it up and output a reference pulse to the ECM. Which would make sense being a hall effect sensor and not a VR sensor, but that's a whole other topic... Glad to hear that part of your issue is resolved.
And as a note, my experience has been that original crankshaft position sensors always seem to be a pain to remove on these. I will unbolt them and then turn them as much as I can back and forth to try and break them free in the bore before trying to pull them out. And worst case if they break apart when trying to pull them out, I will run a wood screw/self tapping screw into them and pull on the screw.