Here's a breakdown of how to troubleshoot and fix this issue:
1. Diagnose the Problem:
* Check the DTC (Diagnostic Trouble Code): Use an OBD-II scanner to get the precise DTC. This will pinpoint the specific problem area. While a "high input" is a general description, the code itself will be more specific.
* Inspect the ECT Sensor: Locate the ECT sensor (usually near the thermostat housing or on the engine block). Visually inspect it for damage, corrosion, or loose wiring connections. A cracked sensor or loose connection is a common culprit.
* Check Wiring and Connectors: Carefully examine the wiring harness leading to the ECT sensor. Look for broken wires, chafing, or corrosion at the connector. A bad ground can also cause this problem.
* Test the Coolant Level: Ensure the coolant level in the radiator is correct. Low coolant can lead to overheating and falsely high ECT readings.
* Check the Thermostat: A malfunctioning thermostat that stays open or closed can affect coolant temperature readings. A stuck-closed thermostat would cause overheating and a high ECT reading.
2. Potential Solutions Based on Diagnosis:
* Replace the ECT Sensor: This is the most common solution. The sensor is relatively inexpensive and easy to replace. Follow the instructions in your vehicle's repair manual for proper installation. Don't forget to disconnect the battery's negative terminal before working on the electrical system.
* Repair Wiring: If you find damaged wires or connectors, repair or replace them. Use electrical tape to insulate repairs properly.
* Replace the Thermostat: If the thermostat is suspected, replace it with a new one of the correct specification.
* Flush the Cooling System: If you suspect excessive corrosion or scale buildup in the cooling system, a thorough flush might help. This should be done after replacing any faulty components.
* Check the PCM: In rare cases, the PCM itself might be faulty. This is less likely but should be considered if other components are working correctly. A PCM replacement is a more involved and expensive repair.
3. Important Considerations:
* Vehicle Year and Engine: The exact location of the ECT sensor and the repair procedure will vary slightly depending on the specific year and engine of your Dodge Grand Caravan. Consult your vehicle's repair manual for precise instructions.
* Professional Help: If you're not comfortable performing these repairs yourself, take your vehicle to a qualified mechanic. Improper repairs can lead to further damage.
* Safety First: Always let the engine cool down completely before working on any components of the cooling system. Coolant is toxic.
By systematically investigating these areas, you should be able to pinpoint the cause of the "high input" engine coolant temperature circuit problem and fix it. Remember to clear the DTC code with your OBD-II scanner after making any repairs to ensure the problem is resolved.
