1. Visual Inspection:
* Location: First, locate the CKP sensor. It's usually mounted near the crankshaft pulley, often on the engine block. Consult your repair manual for the exact location on your specific year and model Cavalier.
* Condition: Check the sensor for any obvious physical damage: broken wires, cracked connector, corrosion, or anything that might indicate a problem. Pay close attention to the connector itself; make sure all the pins are straight and undamaged.
2. Multimeter Testing (Resistance and Voltage):
* Disconnect the sensor: Disconnect the electrical connector from the CKP sensor.
* Resistance Check (if your manual provides resistance specs): Your repair manual should specify the expected resistance between the sensor's terminals. Use a multimeter set to ohms to measure the resistance between the terminals. If the reading is outside the specified range, the sensor is likely faulty. Note: Not all CKP sensors have a specified resistance that can be easily measured with a multimeter. Some have an internal inductive pickup that doesn't give a simple resistance reading.
* Voltage Check (with engine cranking): This is the more useful test.
* Prepare: You'll need a helper to crank the engine (without starting it – only a few seconds of cranking). Make sure the ignition is ON (but not starting).
* Measure: Set your multimeter to AC voltage. Connect the multimeter leads to the two terminals of the disconnected CKP sensor.
* Crank the Engine: Have your helper crank the engine briefly. You should see a fluctuating AC voltage on the meter. If you see no voltage, the sensor, wiring, or the sensor's power supply could be the problem. A weak or intermittent signal might also point to a failing sensor. The voltage level itself isn't as important as the presence of a fluctuating AC signal.
3. Advanced Testing (Oscilloscope):
* Signal Shape: An oscilloscope is the most definitive tool for testing a CKP sensor. It allows you to see the waveform of the signal being produced. A healthy sensor will produce a specific waveform (usually square-ish pulses) corresponding to the crankshaft's rotation. A weak, distorted, or missing signal indicates a faulty sensor. This requires more specialized knowledge and equipment.
4. Troubleshooting:
* Wiring: If the multimeter tests show no voltage even with cranking, there could be a problem with the wiring between the sensor and the engine control module (ECM). Check the wiring harness for breaks, shorts, or poor connections.
* ECM: A faulty ECM could also prevent the sensor from working correctly. This is harder to test without specialized equipment.
* Crankshaft Pulley: If the crankshaft pulley's reluctor wheel (the part that the sensor reads) is damaged or misaligned, it can prevent the sensor from working properly.
Important Considerations:
* Repair Manual: Always consult a repair manual specific to your year and model of 2.2L SFI Cavalier. It will provide crucial details about the CKP sensor's location, connector, testing procedures, and resistance/voltage specifications.
* Safety: Disconnect the negative battery terminal before starting any electrical tests.
* Professional Help: If you're not comfortable performing these tests, take your vehicle to a qualified mechanic. Incorrect diagnosis or repair could lead to further damage.
By following these steps and referencing your repair manual, you'll have a good chance of determining if the CKP sensor is the source of your problem. Remember that a fluctuating AC voltage during cranking is the most significant indicator of a functioning CKP sensor. The absence of any voltage is a stronger indication of a problem.
