Camshaft position sensor determines which cylinder is firing. Then it uses that information to sync the injectors with the ignition. The CPS is one of two sensors that if they fail, your Jeep will not fire the spark plugs or cycle the fuel injectors. Pretty much leaving your Jeep Wrangler or Cherokee sitting dead.
Camshaft position sensor "info"
Where is the CPS Sensor located?
In the Jeep Wrangler YJ & Cherokee XJ, it is located inside the distributor on both the 2.5L & 4.0L.
Will it trigger the check engine light if the sensor is faulty?
Yes it can. Also a defective sensor can cause erratic stalling or not to start all.
Why does it fail?
Heat and vibrations can be reason for failure.
How do you test a Camshaft Position Sensor to see if it’s bad?
Well, to do the most simple test first. Are you getting spark to the plug wires? Here is what I do to test for spark:
Pull the plug wire boot from the plug. Stick a screwdriver into the boot.
Hold the shank of the screwdriver about 1/8" from a ground (close to the block or near-by bracket). The tip of the spark plug that you removed the boot from would be best.
Making sure the Jeep is in neutral. While they hold the brake, have a helper turn the engine over by the ignition. Be careful not to touch the screwdriver shank or the engine block. If there is spark going to the plugs, it will fire you up if you are touching metal!!
Do you have spark? Yes, then the sensor is fine. No spark, time to start testing.
Test the sensor its self.
To test the CPS you will need an analog (old school with the sweeping needle) voltmeter and small paper clips.
Using the small paper clips, straighten and insert them into the backside of the distributor wiring harness connector. Push the wire in until it stops making sure that you have solid contact with the metal connectors.
Connect the red (+) lead to the sensor output wire (terminal #1). Then connect the black (-) lead to the ground wire of the sensor (terminal #2). Set the meter to read DC voltage below 15 volts or so.
Remove the distributor cap. Rotate the engine either by hand until the pulse ring enters the magnetic pick-up on the camshaft position sensor. Rotor button should be pointing at about 8:30 – 9:00 o’clock position.
Turn the ignition key to the “On” position. You should be reading approximately 5 volts. If you are not getting any voltage, check to make sure the meter leads are getting a good connections. Often times the paper clip can move just enough to loose contact with the internal plug terminals. Once you know that you have a solid connection to the terminal and you still have no voltage, need to check for voltage at the CPS voltage supply wire (terminal #3). No voltage there? Check for voltage at pin 7 at the PCM connector.
Crank the engine over by the key. You should see the needle move back and forth from 0 to 5 volts. If you do not get the signal pulse and all wiring checked out fine. Replace the camshaft position sensor.
If you have only a digital multimeter, it will be difficult to test the CPS. You need the old-school analog style so you can watch the needle bounce as it gets a signal. Now, SOME digitals have a bar graph at the bottom of the scale that would bounce to the signal pulses.
So, if ya ain’t got a simple analog. Get ya one cause they are cheap and it never hurts to have an extra Multimeter around.
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