Fault code P2683 – engine coolant bypass valve control circuit high

Fault code P2683 is called “Engine Coolant Bypass Valve Control Circuit High” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2683

Stored code P2683 means that a high signal level has been detected in the engine coolant bypass valve control circuit. This error indicates that the coolant flow control process may be impaired.

This valve regulates the engine coolant flow, which is connected to the cabin heater circuit. Adjustment is based on engine coolant temperature and ambient temperature.

The engine coolant control valve has two positions, “ByPass” and “Link”.

In the “ByPass” position, the coolant in the engine circuit and the heater circuit are separated, and in the “Link” position, the coolant circulates through both circuits. The movement of the valve is controlled by a pulse width modulation signal.

The engine coolant control and adjustment valve uses an internal position sensor. Which sends a signal to the transmission control module to determine the position of the valve.

When the engine coolant temperature rises, the valve teaching procedure is performed. The voltage values at the “Link” and “ByPass” positions must be within the calibrated ranges.

If the PCM polls the valve with values outside the valid ranges, fault P2683 is recorded. Also the fault light on the instrument panel will illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P2683 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

1. Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a malfunction).
2. Engine stalls or starts poorly (especially when starting cold).
3. Floating revolutions, as well as attempts to stall at idle.
4. Overheating of the engine.
5. Black smoke from the exhaust pipe, when working with a rich mixture.
6. Increased NOx emissions may be observed on a lean mixture.
7. Improper operation of the cooling fans.

Fault P2683 is serious, the car will most likely be able to start and continue driving. But it is better to solve it as soon as possible, because improper heat exchange can lead to more serious consequences.

Factors that can cause this error code

The error code P2683 can mean that one or more of the following problems have occurred:

• ECT sensor has failed.
• Coolant temperature sensor circuit is broken.
• Coolant temperature sensor wiring harness or connector is damaged.
• Engine coolant level is low.
• Engine coolant thermostat does not open at proper temperature.
• No adaptation (if required by the manual) was performed after the thermostat was replaced.
• Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P2683

Some suggested steps for troubleshooting and fix the error code P2683:

1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances fault P2683 appeared.
2. Clear the error codes from the computer memory and test-drive the vehicle to find out if the error appears again.
3. Check the coolant level (engine should be cold).
4. Visually inspect the electrical wiring and connections to the sensor for looseness and damage. Repair if necessary.
5. If the ECT sensor has failed, replace it.
6. Test the thermostat; if it has failed, replace it.
7. After replacing the thermostat, perform an adaptation (if required by the manual).
8. Clear the error code from the computer memory again, and test-drive the vehicle to see if the problem is resolved.

Diagnose and repair of problems

The first step in troubleshooting fault P2683, is to review the Technical Service Bulletins (TSB). For known problems with a particular vehicle.

Perform a thorough visual inspection to check the wiring for obvious defects such as scratches, scuffs, exposed wires or burn spots. Next, check connectors and connections for safety, corrosion, and contact damage.

Be sure to carefully check the integrity of the wire harnesses and secure any loose wires. If you find a burned wire, solder it and make sure it is properly insulated.

Check coolant and thermostat

Make sure the coolant level is correct, both in the radiator (when cold) and in the coolant overflow tank. Make sure that there are no leaks and that the sealed cap is working properly.

If there is not enough coolant in the system, the engine may not warm up properly. Because if the temperature sensor is not in contact with the coolant, it will not read the temperature.

Using a non-contact thermometer, or a real-time streaming scan tool, check to see if the engine is warming up properly. Normally, the upper radiator hose should stay relatively cold until the thermostat opens. After that, it will warm up quickly.

If the thermostat is open, the coolant will leak constantly, preventing the engine from reaching operating temperature. This can also be the cause of fault code P2683.

Use a thermometer or diagnostic tool to check the engine temperature after 10 to 15 minutes of operation. If the temperature does not reach the operating temperature, check the ECT sensor.

Check the coolant temperature sensor (ECT)

Visually check the sensor for wiring or connector damage and repair if necessary. Then connect the OBD2 scanner, if the engine temperature is excessively high, about 140°C, this is not normal.

Disconnect the sensor on the engine and see if the reading drops by, say, 10°C. If it does, the sensor is probably faulty, shorted internally, causing a low resistance signal to be sent to the PCM.

But, if you want to be completely sure it’s the sensor and not the wiring, you can do a test. Check the resistance of the sensor against ground with an ohmmeter. The resistance of a normal sensor will vary slightly from car to car.

But basically, if the engine temperature is around 95 degrees Celsius, the resistance will be around 200 ohms. At about -20 degrees Celsius, the resistance will be over 10,000 ohms.

You can use this test to determine if the resistance of the sensor matches your engine temperature. If it doesn’t match your engine temperature, you probably have a faulty sensor.

On which vehicles does this problem occur most frequently

Fault code P2683 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

• Ford (C-Max, Focus)
• Peugeot
• Subaru (Forester)
• Volvo (V50)

Fault code P2683 can sometimes be found with other errors. The most common are the following: P2681, P2682.

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