Fault code P011B – engine coolant temperature/intake air temperature correlation

Fault code P011B is called “Engine Coolant Temperature (ECT)/Intake Air Temperature (IAT) Correlation” 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 P011B

Stored code P011B means that the Powertrain Control Module (PCM) has detected a problem with correlated signals. These signals are between the engine coolant temperature sensor (ECT) and the intake air temperature sensor (IAT).

Fault code P011B – engine coolant temperature/intake air temperature correlation

The temperature sensors on modern engines are of the variable resistance type, which convert temperature into signal voltages. The colder the engine coolant, the higher the resistance. As the coolant temperature increases, the resistance decreases, thereby increasing the signal voltage to the PCM.

It is rare for an engine to have only one coolant temperature sensor. In most cases, one sensor is used to control the thermometer. The other controls the electric radiator fan or the cold start valves in some older systems.

The IAT sensor acts much like the ECT sensor, except with a much narrower range. It only monitors changes in ambient air temperature, not changes in engine cooling temperature.

The IAT sensor is usually located so that ambient intake air can pass through it as it enters the engine intake. The IAT sensor is almost always inserted into the air filter housing or air intake.

If the PCM detects voltage signals from the ECT sensor and IAT sensor that differ by more than a pre-programmed degree. Then code P011B will be stored and the Malfunction Indicator Lamp (MIL) may illuminate.

The MIL on some vehicles will require several ignition cycles in the event of a malfunction.

Symptoms of vehicle malfunctions

The main signal that an error P011B 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 stored as a fault).
  2. Other related fault codes may also be present.
  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 engine.
  6. Excessively rich or depleted exhaust.
  7. Black smoke from the exhaust pipe, when running on a rich mixture.
  8. Excessive NOx emissions may occur when the mixture is lean.
  9. Improper operation of the cooling fans.
  10. Reduced power output of the engine.
  11. Increased fuel consumption.

Error P011B is not a serious error, the car will be able to start and continue driving. But it is better to solve it as soon as possible, because the wrong heat exchange can lead to more serious consequences.

Factors that can cause this error code

The error code P011B can mean that one or more of the following problems have occurred:

  • ECT/IAT sensor has failed.
  • Coolant temperature sensor or inlet air temperature sensor circuit is broken.
  • Coolant temperature sensor or intake air sensor connector harness is damaged.
  • Low engine coolant level.
  • 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 P011B

Some suggested steps for troubleshooting and fix the error code P011B:

  1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P011B 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 relating to the ECT / IAT sensors for looseness and damage. If necessary, repair the faults.
  5. If the ECT / IAT sensors have failed, replace them.
  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 P011B, 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 P011B.

Use a thermometer or diagnostic tool to check the engine temperature after 10-15 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 284°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 car to car.

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 does not match your engine temperature, you probably have a faulty sensor.

Similarly, test the intake air temperature sensor (IAT) to make sure it’s working. And if it is found to be out of order, it also needs to be replaced.

On which vehicles does this problem occur most frequently

Fault code P011B can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chery (IndiS)
  • Chevrolet
  • Chrysler
  • Dodge
  • Ford
  • GMC
  • Honda
  • Hyundai
  • Kia (Picanto)
  • Lexus (GX470)
  • Saab
  • Scion
  • Toyota (4Runner, Corolla, Tacoma, Tundra, Venza)

Fault code P011B can sometimes be found with other errors. The most common are the following: P0115, P0116, P0117, P0118, P0119, P011A.

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