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Old 08-11-2014, 01:10 PM   #1
dagenais
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Crank Shaft Positioning

I search and read a dozen post about the Crank Shaft sensor...

Friend of mine had an accident (everyone is ok) but the car is done... He had just purchased a few part so he gave them to me.

He has both crank shaft sensor (new in box) I was thinking about replacing mine - Have access to hoist for a weekend so brakes, oil etc

Correct me please if Im wrong one sensor in behind the bottom pulley? Can it be replaced with out removing the pulley? Any other tips?

The second is on the block looks easy, remove screw and replace? any tips?

HERE IS the thing I was most confused about the other post, is a relearn process required?

I appreciate your feedback
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Old 08-11-2014, 03:34 PM   #2
AaronGTR
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Why do you want to replace the sensor? Unless you are getting dtc codes that there is a problem with one of them, just leave them alone.


But anyway, no you can't replace the one behind the crank pulley (harmonic damper actually) without removing it. The sensor sits inside the sensor ring that is pressed into the pulley hub and the pulley sits too close to the front cover and oil pan to get to the sensor. You need a special tool to get it off and on as well, and it can be a pain to do with the engine in the car though it can be done.

The crank sensor on the rear of the engine reads a timing ring on the crank shaft and puts out a 7x signal (7 pulses per revolution). That is the base signal for ignition timing and the PCM uses that signal all the time up to red line. The sensor behind the crank pulley is a 24x sensor so it's higher resolution. The PCM only uses that sensor up to like 1600rpm if I recall correctly, so it's only used to control timing at idle and low rpm. The sensor signal needs to be precisely calibrated though to read correct. The timing ring on the crank never moves so the 7x signal is always correct. Any time you remove the crank pulley though when it is replaced there is a possibility it won't be in the same position an sync up with the timing recorded in the PCM anymore. Any time you replace the damper, the sensor, or the PCM you are supposed to do the crank position relearn to make sure the timing is correct at low engine speed.
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Old 08-11-2014, 04:15 PM   #3
dagenais
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dagenais Gettin' there
Aaron thanks again...

just one clarification the 7x sensor is a plug and play no need for any calibration... After you suggestion Im not planning to replace them... I was just thinking have some new parts why not but then again dont want to open a can of worms...
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Old 08-11-2014, 08:42 PM   #4
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Exactly! They don't tend to go bad very often, and if they are working fine right now, no need to replace them. It would be a lot of work for nothing IMO. If you have new ones, just hold onto them for spares if you want in case they ever do fail. And yes, the 7x sensor is just swap and go, no calibration for that one.
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