Fault code P2181 – cooling system performance

Fault code P2181 is called “Cooling System Performance” 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 P2181

This Diagnostic Trouble Code (DTC) is a general powertrain code. Error P2181 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly from model to model.

Fault code P2181 – cooling system performance

Engine temperature is monitored in the cooling system each time the engine is started and serves several purposes. When the engine is cold, the air/fuel mixture is richer, allowing the engine to idle smoothly as it warms up.

The control module (PCM) detects low engine temperatures, which can affect the efficiency of exhaust gas recirculation (EGR). It also detects heat, signaling a problem before the engine overheats.

Unlike most general codes, which are relatively specific to an item or area, the P2181 code is a bit vague. This fault is recognized and set if the engine temperature is out of range.

In this case, the cooling system is either too hot or too cold. That is, the code will be set if the engine temperature reading changes at a rate greater than what the PCM considers normal.

Symptoms of vehicle malfunctions

The main signal that an error P2181 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be memorized as a fault).
  2. The engine temperature gauge shows a temperature higher or lower than normal.
  3. The engine stalls or starts poorly (especially when starting cold).
  4. Floating revolutions, as well as attempts to stall at idle.
  5. Overheating of the vehicle engine.
  6. Abnormal operation of the cooling fans.

Error P2181 is not serious, the car will 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 P2181 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.
  • Sometimes the cause is a defective PCM module.

How to fix or reset OBD-2 code P2181

Some suggested steps for troubleshooting and fix the error code P2181:

  1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P2181 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. Clear the error code from the computer memory again, test drive the vehicle to see if the problem is resolved.

Diagnose and repair of problems

The first step in troubleshooting error P2181, 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 the P2181 trouble code.

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 an OBD2 scanner, if the engine temperature is excessively high, about 280°F, this is not normal.

Disconnect the sensor on the engine and see if the reading drops, like 50°F. 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 vehicle to vehicle.

But basically, if the engine temperature is about 200 degrees Fahrenheit, the resistance will be about 200 ohms. At about 0°F, 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 P2181 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi (A4, Q5)
  • Chevrolet (Cruze)
  • Chrysler (300C, Grand Voyager, Sebring, Town and Country)
  • Dodge (Avenger, Caliber, Challenger, Charger, Grand Caravan, Journey, Magnum, RAM)
  • Hyundai (Solaris)
  • Jeep (Liberty)
  • Porsche (Cayenne)
  • Volkswagen (Beetle, Bora, Eos, Jetta, Passat, Touareg)

Fault code P2181 can sometimes be found with other errors. The most common are the following: P0118, P0128, P0171, P0420, P0442, P2400.

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