How does the crank position sensor have an impact once the truck is running? Isn't that just for cranking / starting the engine?

 

The CKPS sends voltage to the PCM. It's part of the timing circuit and how the PCM monitors engine speed / crank rpms. On some models, the camshaft position sensor is also used as part of the timing circuit as well and, in that case, both affect the timing. On some years / models, the camshaft sensor / advanced pickup module is only used for diagnostic purposes only. It is not part of the timing circuit.

I personally found that both affect my timing as I found out on my vehicle when changing them. Both were either the wrong sensors or bad and, the truck firing sequence was out of phase by a lot. It was stalling out, would not start properly, did not idle, nor accelerate properly.

When the CAM sensor was removed and replaced with OEM, it now started fine however, the new crankshaft sensor caused a loping idle along with incorrect throttle response. It was choking / bogging down when stepped on.

Removing it and replacing it with a clean OEM CKPS, it remedied that issue. So, as you can see, it's not just for starting the car.

 

Thanks. Good info. Is that just on OBDII or is it still used for that on OBDI? Also, say you have a leaking tranny pump where it's spitting tranny fluid, is the sensor in a place that could get coated and gummed and cause this issue? So not necessarily that it is malfunctioning but because of the tranny leak it is not clean and giving bad signals.

 

Regarding the question about OBD I or II, I do not know. Regarding your second question about tranny leak, the answer is no. The sensor is on top of the flywheel on the engine side, isolated from the tranny fluid.

However, if you have a rear main seal oil leak or, for the sake of argument, tranny fluid is passing to your bell housing to the side that houses the starter, why yes, it would be covered at the end in fluid due to the flywheel teeth catching the fluid and throwing it everywhere in the bell housing including the face of the sensor.

However, fluids and rain water are usually not an issue as it uses magnetic pulses to generate a positive DC output voltage. However, if the end is coated in grease that is thick and, loaded with metallic, ferrite particulates, it throws the magnetic pulse cycle off thus creating an imbalance condition / offset in the DC output voltage that feeds to the PCM.

Back to the tranny leak: Do you have tranny fluid leaking from the bell housing flex plate cover? This cover is the same cover that the starter and the tranny support mounts are bolted through. Is there red fluid dripping from this plate?

My guess is a no- it's not dripping from that plate. If this is true, no need to worry about it.

The only way to determine the condition of the CKPS is to physically remove it and check it by eye. Wipe off any particulates, apply a light film of clean light oil to everywhere on the sensor (minus the face), apply light film to the rubber seal and reinstall it. Simple as 1,2,3.

Try that first.

CM

 

Thanks. Again, good info.
I don't want to jack his thread but my problem is a random won't start or shut off. I have a thread started on it. From your description of the CKPS I was wondering if that might be the cause. I'm pretty sure I have a failing fuel pump but, I'll see how the solenoid swap goes. The tranny leak is somewhere around there. I've been told it is a front pump seal. It hasn't leaked enough for me to have it looked at and fixed yet. Need to get a cc paid off then sort it out.

 

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