Several things can cause this code:
* Faulty Coolant Temperature Sensor (CTS): This is the most common cause. The sensor itself might be malfunctioning and sending an incorrect signal.
* Low Coolant Level: While code 31 doesn't directly indicate low coolant, a low level can prevent the engine from reaching the proper temperature. Check your coolant reservoir.
* Thermostat Stuck Open: If the thermostat is stuck open, coolant will constantly circulate without being properly heated.
* Wiring Issues: A problem with the wiring to the CTS can also cause this code. This could be a broken wire, a short, or a loose connection.
* Faulty PCM (Powertrain Control Module): Less common, but a problem with the computer itself could also cause this code.
What to do:
1. Check your coolant level: Ensure the coolant reservoir is filled to the correct level.
2. Check the coolant temperature sensor: This often requires a multimeter to check its resistance at various temperatures. A replacement is relatively inexpensive and easy to install. Look up a tutorial specific to your 1997 Grand Caravan engine.
3. Inspect the wiring: Check the wiring harness leading to the CTS for any damage or loose connections.
4. Consider the thermostat: If the engine is consistently running cold, even with adequate coolant, a stuck-open thermostat is a likely suspect. This usually needs to be replaced.
If you're not comfortable diagnosing and repairing this yourself, take your Grand Caravan to a mechanic for proper diagnosis and repair. Ignoring a coolant temperature issue can lead to more serious engine problems.
