Can you be more specific on that fault code? One common code is for "Engine coolant staying cold too long". That is a thermostat issue. I do know that in the northern climates, every Chrysler product will have that code in winter. It's due to extended idling to warm up the engine. The code sets if the coolant doesn't reach a specific temperature within six minutes of starting the engine. It won't reach that temperature in time if idling, but that code doesn't turn on the Check Engine light. Other manufacturers may have a similar strategy for that fault code. The clue to a thermostat problem is you'll get cool or cold air from heater well after the engine has been running a while.
A different fault code can be, "Engine Coolant Temperature Sensor Voltage too Low, (or "too High)". On older cars, they used two coolant temperature sensors; one for the Engine Computer and one for the dash gauge. On cars as new as yours, there's just the one sensor that feeds the Engine Computer. That computer sends the information to the Body Computer, then to the instrument cluster, which is another computer module. That's why you're getting multiple symptoms from just one sensor circuit.
In most applications, temperature sensors are supplied with 5.0 volts from the Engine Computer, then they drag it down to between roughly 0.5 volt when real hot to 4.5 volts when cold. By far the most common problem with this circuit is a cut wire or corroded connecter terminal. Those cause an "open circuit", meaning a broken circuit. That is the only way the signal voltage can go to 5.0 volts. Since that is outside the acceptable range of 0.5 to 4.5 volts, it triggers a fault code, in this case, "ECT Voltage too High".
I know we should never say never, but it is virtually impossible for a temperature sensor to be shorted. The exceptions are if it has physical damage that causes the two leads of its internal resistor to short together, or if there's a real lot of corrosion between the connector terminals. The much better suspect for a fault code for "ECT Voltage too Low" is the wire is bare in a spot and is shorted to ground, meaning the engine or body. Wire harnesses are usually pretty well protected against that, so look for any place the harness has been repositioned, such as during crash repair, or it was moved for some other service, and now a wire has rubbed through where it is laying on the sharp edge of a metal bracket. If the wire is shorted to ground, it will drag the signal voltage down to 0 volts, which is also outside the acceptable range. Either condition, too high or too low, will set the appropriate fault code, and that is when the Engine Computer knows it can't trust the readings from that sensor. In response, it turns on the radiator fan just in case the engine is getting too hot. That insures the engine won't overheat.
This diagram is part of the Power Train Management System. It includes the coolant temperature sensor. The wire in question is listed as a yellow wire. You know where that sensor lives now. Start there and try to follow the harness to see if there's a place where it might be rubbed through. Also consider having a helper watch the dash gauge while you move and wiggle the harness in various places. Be careful when you do that. The goal is not to shake it so vigorously that the defect disappears because that doesn't really fix anything. The problem could come back in the future. The goal is to disturb it just enough to get an indication you're changing something. That tells you you're in the right area. That narrows down the places to look for a defect.
You also might look at this article:
https://www.2carpros.com/articles/how-to-check-wiring
to get an idea of the things we look for when dealing with electrical problems. Intermittent problems are the worst and the most frustrating. They become easier when you have something to look at to see when you're affecting the circuit, in this case, the dash gauge.
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Thursday, December 3rd, 2020 AT 1:02 AM
