1. The Crankshaft Position Sensor (CKP Sensor): This is the most likely culprit. The CKP sensor sends a signal to the computer based on the crankshaft's rotation, which is directly related to engine RPM.
* Check: Inspect the sensor for physical damage (broken wires, corrosion, etc.). Use a multimeter to check its output signal while cranking the engine. You should see a fluctuating voltage. A bad sensor will often show no signal or a weak, erratic one.
* Replace: If faulty, replace the CKP sensor. It's relatively inexpensive and easy to access (location varies slightly depending on engine type; consult a repair manual).
2. The CKP Sensor Wiring: Even if the sensor is good, damaged wiring can interrupt the signal.
* Check: Visually inspect the wiring harness leading to the CKP sensor for breaks, shorts, or corrosion. Use a multimeter to check continuity and resistance in the wires.
* Repair/Replace: Repair any damaged wiring or replace the harness section if necessary.
3. The Computer (PCM/ECM): While less likely, a faulty engine control module (PCM or ECM) could be preventing the signal from being properly interpreted or transmitted. This is a more involved diagnosis and usually requires professional equipment.
* Check: This is usually best left to a professional mechanic or diagnostic technician. They'll likely use a scan tool to check for diagnostic trouble codes (DTCs) that might point to a PCM issue.
* Replace: Replacing the PCM is expensive and should be a last resort after ruling out other possibilities.
4. The OBD-II Connector: A loose or damaged connection at the OBD-II diagnostic connector could interfere with the signal reaching the smog equipment.
* Check: Ensure the connector is firmly seated and free from corrosion or damage. Clean the connector contacts with contact cleaner if necessary.
5. The Ignition System: A weak or faulty ignition system can sometimes affect the CKP sensor's signal.
* Check: Check the ignition coil, spark plugs, and distributor cap and rotor (if applicable). A failing component can create irregular engine operation, indirectly impacting the RPM signal.
Before you start replacing parts:
* Check for other diagnostic trouble codes (DTCs): Use an OBD-II scanner to retrieve any stored trouble codes. This can help pinpoint the problem more accurately.
* Consult a repair manual: A repair manual specific to your 1995 Chrysler Sebring LXi will provide detailed information on the location of the CKP sensor, wiring diagrams, and diagnostic procedures.
Important Note: If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair. Improperly working on the electrical system can cause further damage.
