The crankshaft position sensor in my 97 Jeep Cherokee has packed up.
The sensor has a 5v supply, it then sends a smaller voltage to the PCM (0.5v - 5v) according to the position of the magnet in the sensor.

Obviously the sensor has set output values depending on the engines Revs.
Therefore, my question to everyone is whether it would be possible to design a circuit that 'mimics' the Crankshaft position sensor output?
By tapping into the tachometer signal for the engine RPM and synchronising set RPM values to set voltage outputs would one be able to fool the PCM into thinking that there is a CPS and that its working?

Thanks for your help!

 

I am not an engineer but I will say this,your tach,injectors,timing all get there signal from your cps and it is counting holes as they pass by,and adjusting everything based on rpm,I am pretty sure it is not possible

 

So you're saying that the tachometer gets its data from the CPS, not from another source?

Is that a fact or are you assuming? Im just double checking so Im sure!
No offense meant!

Thanks for your timely response!

 

My understanding of it is all other parts of the way a 4.0L get there signal from the CPS.

So there is no way to by-pass or "fake" a CPS signal.

 

your engine cannot run without the cps installed and working.

 

Ok. Thanks for all the help!
So I have no choice but to buy a new one then! Pity - thought I could save a few bucks!

Anyway... Thanks again!

This forum rocks! Response time is excellent!

 

No offense taken,it is a fact though that all cars get there signal for the tach from the coil,pcm,or cps. if your car has a crank shaft positoner it is used to send signals to the first two,so weather the signal comes directly from the cps or not,it is what starts everything in motion. Before cars had a cps the tach got its signal from the coil,and flex plates did not have tone rings.

 

you can get a kit to change the cps to the front
for easier access and tuning but it will cost you

 

The CPS works with the Hall effect, like an electric guitar pick-up or an ABS sensor, and produces a square wave signal. The teeth and notches proximity on the phonic wheel on the flywheel cause a magnetic feild changement in the sensors magnet, that induces a current flow in an electric conductor and generates the square wave (transducer). The CPU reads the signal frequency and intensity and calculates the rpm. There are also some bigger notches on the wheel that produce a longer 0 signal in between and are used by the CPU to trigger the ignition coil.
The cps has therefore a double function, and it's functionality is linked to the dynamics of the engine.
If you had a double channel Fluke wave generator with frequency sweep and a Tektronix 640 oscilloscope to sinchronize it with some sort of RPM input, it could be possible to emulate the cps signal in theory, but absolutely not worth doing it.
There are many other awesome things you could do with this kind of transducers, i'll give you a hint: ABS.. lockers...ABS..lockers!!!

 

Wow, i think i freezed this thread with my last post...

 

fantic...you are PURE GENIUS!!

 

like ice.

 

There were some CPS sensors that were mounted to the front of the engine at or replacing the harmonic balancer. That company went out of business though. There may still be some around. Hesco sold them at one time.

 

sounds more difficult to accomplish your idea then to just replace the CPS

 

These are very common on european cars, i installed one of these (taken from a Fiat together with its coil packs) on a suzuki 1.6 twin cam 16v engine from a Swift) to eliminate the distributor, that sticks out horizontally from the back side of the head and would not fit in a Suzuki samurai engine bay unless u make a huge hole in the firewall panel and have it instead of the radio.
It worked fine, and i made also an adjustment of the sensor making oval holes on it to slide it up and down around the bolts and change the timing, actually a cheap mod we could all do on our CPS on the Jeeps too.