Unique Cam Sensor Failure

Caleb Technician Mishawaka, Indiana Posted   Latest   Edited  
Discussion
Driveability
2015 GMC Terrain SLE 2.4L (K LEA Flex) 6-spd (6T45)
P0366 - Camshaft Position Sensor "B" Circuit Range/Performance Bank 1

Sorry guys I made a mistake embeding the files. The first file is actually the good one after repairs. The bad one is on the bottom. This was an easy diag. However for discussion purposes and to satisfy my curiosity I would like to see if I can get some in depth answers on the way this sensor failed. This vehicle came from another dealer. They had already replaced both VVT solenoids. I do not know if this was the original code. It had a current P0366 which is Bank 1 exhaust cam sensor performance. Without typing a big story the code description is too many or too little pulses from the cam sensor in question in a certain amount of time based on the crank speed and rotation. Anyway P0366 was current so I connected the Pico to the crank, both cam signals, and the 4th channel to ground on the exhaust cam sensor Red: Exhaust cam signal . Yellow: Intake cam signal. Green: Crank sensor signal. Anyone who has ever scoped a GM 2.4 knows that the reluctor wheels on both cams are identical,so immediately my problem was obvious. We removed the cam sensor and of course it was a Dorman. 

diag​.​net/file/f6658x8ej…

Anyway my question is this? Usually when I see a sensor failure its not repetitive in nature like this. This pattern was repititive like this everytime. When I first saw it I started questioning the reluctor. However the tech who was working on the car already had the valve cover off when he asked me to help him diag it. So I saw the reluctor before and I knew it was okay. Anyway after thinking about it and comparing it too the intake with some cursors it became evident that the sensor was not picking up small time base pulse changes. Im not sure how to word that any better. Basically the sensor only changed when the amount of time at 5volts or 0 volts was long enough for it too respond. Anyway thats my theory. If you put cursors on it and compare to the intake, it matches perfectly if you can remove the short pulses from your mind and look at the overall picture. Anyway Im curious as too what caused the sensor to react that way. You would think if it can see one transition it can see them all. Thanks for any input! 

diag​.​net/file/f5468yv31…

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Marlin Technician
Estacada, Oregon
Marlin Default
 

My guess is extremely low quality transistor with slow switch time. Or, possibly there is too much plastic on the end, resulting in the magnetic field being very borderline for switching. I just cannot get over the insanity of using such Dorman parts.

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Angel Technician
Boston, Massachusetts
Angel Default
 

Oh Dorman, I could be completely wrong but my guess would be a sensor gap issue. Nonetheless great diag. Like you say its simple but to those that don't believe in scoping. What would be there next step? Thanks for sharing

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Yes I dont know what most peoples next step would be. In this particular situation I overheard the tech working on it quoting a camshaft. Needless to say I asked a few questions and this is what happened lol.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Most people would have seen "sensor" in the DTC wording and replaced the sensor and been done. Scoping lead to an interesting pattern discussion, but would have caused most guys to tear down the engine needlessly. This is actually a great example of how scoping can just add to the confusion.

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Marlin Technician
Estacada, Oregon
Marlin Default
 

Uh, yeah, like maybe try another Dorman sensor? I disagree with a scope adding to the confusion; ignorance causes confusion in such cases.

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

I guess I would have to respectfully disagree Geoff. All you have to do too rule out a reluctor issue is swap the intake an exhaust cam sensors. The only possible reason for confusion here was the perfect repetitive nature of the failure. If it was in the least way not repetitive the sensor would be a no brainer. I fail to see how this engine would have needed teardown after using the scope? Can…

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