Possible Causes:
* Faulty ECT Sensor: This is the most common culprit. The sensor itself may be malfunctioning, providing an inaccurate reading. It's relatively inexpensive and easy to replace.
* Wiring Issues: A break in the wiring harness leading to the ECT sensor, a short circuit to voltage, or corrosion in the connector can all cause a high voltage reading. Inspect the wiring carefully for damage.
* Faulty PCM: While less likely, a problem with the PCM itself could also cause this code. This is usually the last thing to suspect and is more expensive to diagnose and repair.
How to Fix it:
1. Check the ECT Sensor: This is the first step. The sensor is usually located on the engine block near the thermostat housing. It's a small sensor with one or two wires connected to it.
* Visual Inspection: Look for any obvious physical damage to the sensor.
* Resistance Test (Optional but recommended): You'll need a multimeter to test the resistance of the sensor. The resistance should change with temperature. Compare your readings to the specifications in your vehicle's repair manual. A drastically different resistance or no change in resistance indicates a faulty sensor. Note: The sensor must be disconnected from the wiring harness for this test.
* Replacement: If the sensor is damaged or the resistance test fails, replace the ECT sensor with a new one from a reputable auto parts store. Make sure to get the correct part number for your specific engine.
2. Inspect the Wiring Harness: Carefully examine the wiring harness from the sensor to the PCM connector. Look for any:
* Broken wires: Repair or replace any damaged wires.
* Corrosion: Clean any corrosion from the connector using electrical contact cleaner.
* Shorts to voltage: Look for any areas where the wiring might be touching metal parts of the engine.
3. Clear the Code: After replacing the sensor or repairing the wiring, clear the trouble code using an OBD-II scanner. Then, run the engine to see if the code returns. If the code persists after this, you may have a more serious problem.
4. PCM Diagnosis: If the code persists after checking the sensor and wiring, you may need to have the PCM diagnosed by a professional mechanic. This is the least likely cause, but is often the most expensive to resolve.
Important Notes:
* Repair Manual: A repair manual specific to your 1998 Chevy Cavalier is highly recommended. It will provide detailed diagrams, specifications, and troubleshooting steps.
* Safety: Always disconnect the negative battery terminal before working on any electrical components in your vehicle.
* Professional Help: If you are not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair.
By systematically checking these components, you should be able to identify and fix the cause of the P0118 code on your Chevy Cavalier. Remember to always prioritize safety and consult your repair manual for specific details regarding your vehicle.
