What does the crank sensor "talk" with
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Senior User
Joined: Oct 2011
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Crank Sensor / Tone wheel
Okay, here's the deal. I have a 4bt (3.9 cummins diesel) i'm putting in my 2003 F150 supercrew. There is a kit out there that is 285.00 to make my tack work. It is simply a wheel that bolts to my harmonic balancer and has a probe that counts the teeth or lack of metal as it rotates. I have the probe off of my 4.6 L ford engine. How many pulses does it need to count. I'm clueless there, but i thought i might have a wheel cut out with the proper teeth and use my ford probe to see if it works! Any Help there? I still have my gas harness and could plug it right in.
Logistics Pro
Joined: Jan 2001
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From: Central NYS
The 4.6L Ford uses a 35 tooth sensor ring to excite the crank sensor (which is a variable reluctance type sensor).
The teeth on the sensor ring are 10* a part and the "36th tooth" is missing.
(The missing tooth is how the PCM knows when cyl #1 is at TDC. So, the crank sensor lets the PCM know when cyl #1 is at TDC, but that crank sensor can't determine if cyl #1 is at TDC on the compression stroke or TDC on the exhaust stroke. That's the job of the cam sensor.)
The teeth on the sensor ring are 10* a part and the "36th tooth" is missing.
(The missing tooth is how the PCM knows when cyl #1 is at TDC. So, the crank sensor lets the PCM know when cyl #1 is at TDC, but that crank sensor can't determine if cyl #1 is at TDC on the compression stroke or TDC on the exhaust stroke. That's the job of the cam sensor.)
Thread Starter
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Senior User
Joined: Oct 2011
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The 4.6L Ford uses a 35 tooth sensor ring to excite the crank sensor (which is a variable reluctance type sensor).
The teeth on the sensor ring are 10* a part and the "36 tooth" is missing.
(The missing tooth is how the PCM knows when cyl #1 is at TDC. So, the crank sensor lets the PCM know when cyl #1 is at TDC, but that crank sensor can't determine if cyl #1 is at TDC on the compression stroke or TDC on the exhaust stroke. That's the job of the cam sensor.)
The teeth on the sensor ring are 10* a part and the "36 tooth" is missing.
(The missing tooth is how the PCM knows when cyl #1 is at TDC. So, the crank sensor lets the PCM know when cyl #1 is at TDC, but that crank sensor can't determine if cyl #1 is at TDC on the compression stroke or TDC on the exhaust stroke. That's the job of the cam sensor.)
Logistics Pro
Joined: Jan 2001
Posts: 3,740
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From: Central NYS
Depending on what year FORD (assuming an F150 here), what transmission, what instrument cluster, etc, the PCM will digest the frequency of the CKP sensor for the PCM's purposes of controling the engine (i.e, spark advance, logging fuel trims, etc). I'm not sure if the PCM passes on the original Hz of the CKP or a digested version of it, to the Instrument Cluster Module.
The ICM's job it is to grab signals from the network and modify them in order to control the vaious guages and indicator lights within the instrument cluster.
Lead Driver
Joined: Sep 2006
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The crank sensor is so desgnated because it is a referance signal for many applications.
This single signal is used by the PCM for ignition reference, idle speed corrections, RPM indicator, missfire monitoring and a number of other applications within the PCM program.
The dash has it's own micro processor that takes a number of signals from the PCM to derive it's functions.
Trying to get your dash tach and speedo to work accurately would take a bit of work to get the right signals to the input of the dash.
The PCM program has an information line and word that sets the speed reading according to tire size. It's all digital division and conversion used by a number of seperate outputs.
In trucks that have PATS, the PCM 'merrys' the Dash by code and key programming.
I think your better off going to new seperate gauges unless you know how the Ford system works and can re-engineer a signal interface to satify the dash requirements.
Good luck.
This single signal is used by the PCM for ignition reference, idle speed corrections, RPM indicator, missfire monitoring and a number of other applications within the PCM program.
The dash has it's own micro processor that takes a number of signals from the PCM to derive it's functions.
Trying to get your dash tach and speedo to work accurately would take a bit of work to get the right signals to the input of the dash.
The PCM program has an information line and word that sets the speed reading according to tire size. It's all digital division and conversion used by a number of seperate outputs.
In trucks that have PATS, the PCM 'merrys' the Dash by code and key programming.
I think your better off going to new seperate gauges unless you know how the Ford system works and can re-engineer a signal interface to satify the dash requirements.
Good luck.
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Senior User
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thanks, but i'm still searching here
The crank sensor is so desgnated because it is a referance signal for many applications.
This single signal is used by the PCM for ignition reference, idle speed corrections, RPM indicator, missfire monitoring and a number of other applications within the PCM program.
The dash has it's own micro processor that takes a number of signals from the PCM to derive it's functions.
Trying to get your dash tach and speedo to work accurately would take a bit of work to get the right signals to the input of the dash.
The PCM program has an information line and word that sets the speed reading according to tire size. It's all digital devision and conversion used by a number of seperate outputs.
In trucks that have PATS, the PCM 'merrys' the Dash by code and key programming.
I think your better off going to new seperate gauges unless you know how the Ford system works and can re-engineer a signal interface to satify the dash requirements.
Good luck.
This single signal is used by the PCM for ignition reference, idle speed corrections, RPM indicator, missfire monitoring and a number of other applications within the PCM program.
The dash has it's own micro processor that takes a number of signals from the PCM to derive it's functions.
Trying to get your dash tach and speedo to work accurately would take a bit of work to get the right signals to the input of the dash.
The PCM program has an information line and word that sets the speed reading according to tire size. It's all digital devision and conversion used by a number of seperate outputs.
In trucks that have PATS, the PCM 'merrys' the Dash by code and key programming.
I think your better off going to new seperate gauges unless you know how the Ford system works and can re-engineer a signal interface to satify the dash requirements.
Good luck.
I really appreciate the answers and i am thankful for your knowledge base. The deal is that i've been told that the Factory Tach must function so that the AC compressor can be controlled by the stock PCM. As i've mentioned, there's a tach kit that is plug and play, but its $300. I'm definitely going to need the AC for family road trips in South Mississippi. If i don't need the tach to make my AC compressor work, then yes an aftermarket is the way to go. What say you? If i understand correctly, the tach signal IS coming from the crank sensor and NOT the coil. IF that is so, i can have someone build the tone wheel and spacer i need and i can fab up a bracket to use my existing crank sensor and be plug and play.
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Lead Driver
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I don't know of any hard association of the PCM with the A/C.
They are seperate functions.
The only thing that happens is the A/C has a signal input to the PCM to raise the idle control to prevent misc. stalling as A/C compressor loads change..
This is a minor function your new setup may handle ok..
Good luck.
They are seperate functions.
The only thing that happens is the A/C has a signal input to the PCM to raise the idle control to prevent misc. stalling as A/C compressor loads change..
This is a minor function your new setup may handle ok..
Good luck.
Thread Starter
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Senior User
Joined: Oct 2011
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I don't know of any hard association of the PCM with the A/C.
They are seperate functions.
The only thing that happens is the A/C has a signal input to the PCM to raise the idle control to prevent misc. stalling as A/C compressor loads change..
This is a minor function your new setup may handle ok..
Good luck.
They are seperate functions.
The only thing that happens is the A/C has a signal input to the PCM to raise the idle control to prevent misc. stalling as A/C compressor loads change..
This is a minor function your new setup may handle ok..
Good luck.
Yes, i suppose i could get it all installed and see what happens without that signal. I do want a tach and can get the tone wheel etc for around $100 and use my prob. Factory tach would be nice. The point im trying to clarify is that the tach signal DOES come from the crank sensor, correct?
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
I don't know of any hard association of the PCM with the A/C.
tach signal DOES come from the crank sensor, correct?
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Senior User
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Great, now were moving along!
Since the crank sensor communicates with the PCM, i need to keep that functioning. I have looked around and read through some of your posts and the device we are talking about with 35 teeth (#36 missing) is called a Reluctor ring. Now that would mean both the 5.4 and 4.6 have this same ring. If i can find one in a salvage yard, i can make my stock sensor work with it by making an adapter to fit it to my harmonic balancer and i should be in business. Anyone have a part number on that ring?
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