How To: Change CPS + My CPS Blurb - Ford Powerstroke Diesel Forum
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post #1 of 4 Old 03-01-2012, 10:22 AM Thread Starter
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How To: Change CPS + My CPS Blurb

Given how common CPS failures are, I felt a video was necessary. But, its pretty easy, so the last 1/2 of the video is me talking about the CPS and its basic functions.


In the video I talk about the CPS detecting the teeth on a gear. This is the gear in question. Notice the square holes in the gear? This is actually what the CPS is detecting, no the teeth. You will also notice that 2 of the squares are different sizes. These identify cylinder 1 and 4 to the CPS



Quote:
Originally Posted by Ford Manual
The PCM receives engine rotational position information from the Camshaft Position (CMP) sensor. The CMP is a hall-effect device. It outputs 12 volts to the PCM whenever it detects the iron of a spoked target wheel in front of it, and it outputs 0 volts whenever it detects the space between the spokes. The target wheel spokes and spaces are each 15 crank degrees, except for narrow spoke which indicates cylinder No. 1 and a wide spoke which indicates cylinder No. 4 (fires 5th). The NGS PID RPM is generated by the PCM from the CMP signal.
Thank you to mueckster for the manual citation, and SnackDoc for the picture.
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post #2 of 4 Old 03-01-2012, 11:50 AM
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Well, I think saying there's "very little difference between the Grey & Black" is a bit misleading though....

I assume you've seen this -> Black, Grey, & Dark Blue Cam Position Sensor Perdels Test - Diesel Forum - TheDieselStop.com

Clearly some significant differences. Don't think it has anything to do with the thickness of the plastic, IIRC there was talk of an internal diode being less sensitive to failing with heat in newer Grey ones (not positive, but I do remember something like that from years ago...)

I totally agree with your point about Grey being a suitable substitute for most people and think WAY Too Much has been made of the superiority of a Black one (although I've yet to take my Black one out and have a black spare so, I may Never know )

The picture of the reluctor in the gear is Very interesting!
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post #3 of 4 Old 03-01-2012, 11:54 AM Thread Starter
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Quote:
Originally Posted by NoRalPh View Post
Well, I think saying there's "very little difference between the Grey & Black" is a bit misleading though....

I assume you've seen this -> Black, Grey, & Dark Blue Cam Position Sensor Perdels Test - Diesel Forum - TheDieselStop.com

Clearly some significant differences. Don't think it has anything to do with the thickness of the plastic, IIRC there was talk of an internal diode being less sensitive to failing with heat in newer Grey ones (not positive, but I do remember something like that from years ago...)

I totally agree with your point about Grey being a suitable substitute for most people and think WAY Too Much has been made of the superiority of a Black one (although I've yet to take my Black one out and have a black spare so, I may Never know )

The picture of the reluctor in the gear is Very interesting!
I just added a note to the video, because it was pointed out that I made it seem like the Grey CPS was very prone to failure, which is not true. It does last longer than the Black.

Also, I was told that the difference between the Grey and black was not plastic depth but size of the magnet. I still recall reading that the plastic got thicker on the grey, but it's probably also true that the magnet became less pronounced.

There is definitely lots of speculation and good discussion is ALWAYS encouraged!
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post #4 of 4 Old 03-01-2012, 12:19 PM
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Quote:
Originally Posted by TreySpooner65 View Post
I was told that the difference between the Grey and black was not plastic depth but size of the magnet. I still recall reading that the plastic got thicker on the grey, but it's probably also true that the magnet became less pronounced.
Yea but, that's not what goes wrong... It's not about the strength of a magnetic field but the failure of the circuity that causes the Black one to be prone to dying.

The Hall Effect produces a square wave variance in voltage that, for some reason I'm not 100% sure of, is completely interrupted with a change in temperature of a failing Black CPS (typically a 10-15min cool down restores it) and the Grey design actually cured that problem (they still fail of course, like anything else). But that was the Blacks downfall. The new Grey design drastically changed something else though in the way that square wave is seen by the PCM and introduced it's own peculiarities

I'm sure there's somebody out there who actually knows the specific reason the Black CPS fails. What "goes wrong" that then cures itself with temperature. Maybe it was diode related, maybe not, but it Is some component inside that goes "open/short" to stop the signal. Maybe they'll come and enlighten us both
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