How The Crankshaft position Sensor Works

The crankshaft place sensor, on your GM 4.3L, 5.0L, or 5.7L Vortec engine is a room Effect form sensor, i beg your pardon in level English method that it needs a power and a Ground source to create a signal.

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Once the crank sensor produces this signal, the signal is an on/off voltage signal (in DC Volts).

Below, in a nutshell, is just how the crankshaft place sensor works in your 4.3L, 5.0L, and also 5.7L Chevrolet or GMC (or Olds, Cadillac) pick Up or SUV:

When you revolve the vital and start cranking the engine the crank sensor gets 12 Volts ~ above Circuit A and also Ground top top Circuit B.A round ‘target wheel’ attached to the prior of the crankshaft and positioned so the it rotates over and in near proximity come the crank sensor, starts to rotate.As the ‘teeth’ ~ above this target wheel happen by the crank sensor, they begin to activate the sensor into developing an ON/OFF Pulse.ON is as soon as a tooth on the target wheel passes straight over the sensor, i m sorry induces the sensor to create and send a 5 Volt DC pulse. Off is as soon as that exact same tooth passes totally away from the crank sensor, which reasons the sensor to drop the voltage under to 0 Volts.The PCM uses these ON/OFF 5 Volt pulses to start activating the ignition manage module and a organize of other things to acquire your vehicle started.

The most essential thing to know around the crank sensor is that if the goes bad, your GM pick Up or SUV will certainly "crank however not start" due to a absence of spark and fuel injection.

In mine crankshaft position sensor check instructions, I"ll asking you to manually rotate the crankshaft sheave by hand since this is the only way that her multimeter will have the ability to see this ON/OFF voltage pulses. Utilizing the starter motor will make the multimeter average out these pulses and also this form of test an outcome is no as accurate.

TEST 1: testing The CKP Signal through A Multimeter

The crankshaft position sensor is located on the bottom (passenger-side) the the engine time chain cover. The very very first thing you"ll should do is to verify if the crank sensor is producing a crank signal.

This is a really easy, but accurate test, that will verify the performance of the CKP sensor. But remember (and I recognize that by currently I"m starting to sound like a broken record), this accuracy is accomplished by measure the crank sensor signal v a multimeter and manually turning the engine by hand, since cranking the engine v the starter motor would not accomplish the same result (unless you usage an oscilloscope).

NOTE: The crankshaft place sensor need to remain associated to its electric connector to read the CKP signal. You"ll have to use a back probe on the connector or a cable piercing probe ~ above the wire. You deserve to see an instance of this tool here: Wire Piercing Probe.

OK, here"s the test:


Raise the prior of the choose up or SUV and then reduced it ~ above jack stands. This will also allow you to comfortably crank the engine manually using a 1/2 ratchet and also the proper socket.


Disable the fuel system. One way of law this by disconnecting the Spider fuel injector connector.This is important! through disabling the fuel injectors, you"ll save the car from possibly beginning as you do the crank sensor test.


Disable the ignition system. You have the right to easily accomplish this by simply disconnecting the ignition coil or the ignition control module. This will prevent the ignition system from producing spark.


Connect the red multimeter test cause the wire labeled through the letter C in the photo above (with an proper tool, favor a wire-piercing probe).The cable (circuit) labeled v the letter C is the one the transmits the CKP sensor signal to the PCM.


Connect the black color multimeter test result in the battery negative (-) terminal.If you decide to affix the black multimeter test result in a Ground suggest somewhere under the vehicle, make certain it"s a quite clean and also rust-free spot.


Manually revolve the engine by hand using a 1/2 customs ratchet and also a socket ~ above the crankshaft sheave (turn that clock-wise).


Your multimeter will certainly register an ON/OFF voltage signal together you turn the crankshaft pulley.ON is once the multimeter displays 5 Volts DC and also OFF is once it displays 0 Volts (0.1 Volt equates to 0 Volts).

Let"s translate the outcomes of your Crank Sensor Signal Test:


CASE 1: The multimeter registered the ON/OFF voltage as you turned the engine v the ratchet. This is the correct test an outcome and the confirmes the the crank sensor is functioning properly and creating a CKP signal.

No further testing is required since the various other two tests in this post check that the crankshaft place (CKP) sensor is acquiring power and also Ground. Because your check confirms that the CKP sensor is producing a signal, then it also proves that it"s getting power and also Ground.

If girlfriend need aid diagnosing the no start condition on her vehicle, the complying with tutorial may be the help:

CASE 2: The multimeter DID not register the ON/OFF voltage signal as you rotate the engine v the ratchet. This test an outcome usually confirms that the crankshaft position sensor is bad and needs to it is in replaced. Around 90% of the time this is hitting the nail on the head, yet I recommend the you examine that the sensor is likewise getting power and Ground too.

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By testing and confirming that the CKP sensor is getting power and Ground, you"ll have the ability to decisively check it is negative or that maybe one more issue exists, go to: test 2: Making sure The CKP Sensor Is getting Power.