Fault code P00B7 – engine coolant flow low/performance

Fault code P00B7 is called “Engine Coolant Flow Low/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 P00B7

Diagnostic code P00B7 means that the Powertrain Control Module (PCM) has detected a mismatch in the signal correlation between the coolant temperature sensor (CTS) and the engine coolant temperature sensor (ECT). This data is perceived by the PCM as limiting engine coolant flow.

Fault code P00B7 – engine coolant flow low/performance

To ensure that the coolant flows between the radiator and the engine coolant passages as intended, the PCM monitors the coolant temperature in the radiator and the engine coolant passages. The PCM monitors the coolant temperature in the radiator and compares it to the engine coolant temperature.

The ECT sensor usually consists of a thermistor that is immersed in solid resin and sealed in a metal or plastic housing. Brass is the most popular of these housing materials because of its durability.

The thermal resistance level of the ECT sensor decreases as the coolant heats up and flows through it. This causes the voltage in the ECT sensor circuit to increase, which it transmits to the PCM.

As the engine cools, the sensor resistance increases, causing the voltage in the ECT sensor circuit to decrease. The PCM recognizes these voltage fluctuations as a change in engine coolant temperature.

The radiator coolant temperature sensor monitors temperature in much the same way as the ECT sensor. It is usually inserted into one of the radiator sections, but can also be installed in a pressurized coolant reservoir.

If the PCM detects voltage signals from the ECT sensor and radiator coolant temperature sensor that differ by more than the maximum allowable parameter. Code P00B7 will be stored and the Malfunction Indicator Light (MIL) may illuminate.

It may take several cycles of driving with the fault to illuminate the MIL.

Symptoms of vehicle malfunctions

The main signal that an error P00B7 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 memory as a malfunction).
  2. The engine stalls or starts badly (especially when starting cold).
  3. Floating revolutions, as well as attempts to stall at idle.
  4. Overheating of the vehicle engine.
  5. Incorrect or false temperature readings.
  6. Increased fuel consumption.
  7. Black smoke coming out of the exhaust pipe, if the mixture is rich.
  8. Increased NOx emissions may be seen with lean mixture.
  9. Abnormal operation of the cooling fans.

Error P00B7 is not very serious, the car will be able to start and continue driving. But it’s 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 P00B7 can mean that one or more of the following problems have occurred:

  • Low coolant level.
  • Stuck thermostat.
  • Defective engine coolant temperature sensor (ECT).
  • The radiator coolant temperature sensor (CTS) has failed.
  • The coolant temperature sensor wiring harness or connector is damaged.
  • Blown fuse.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P00B7

Some suggested steps for troubleshooting and fix the error code P00B7:

  1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P00B7 appeared.
  2. Clear the error codes from the computer memory and test-drive the vehicle to find out if error P00B7 appears again.
  3. Check the coolant level (engine should be cold).
  4. Visually inspect the electrical wiring and sensor connections for looseness or damage. Repair if necessary.
  5. If the ECT or CTS sensor has failed, replace it.
  6. Inspect the fuses; if there are blown fuses, replace them.
  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 P00B7, is to review the technical service bulletins (TSB). For known problems with your 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 P00B7.

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 CTS sensor.

Check the coolant temperature sensors

Visually check the sensors for wiring or connector damage and repair if necessary. Then connect an OBD2 scanner, if the radiator temperature is excessively high, about 284°F, this is not normal.

Disconnect the sensor 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 transmitted 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.

With this test, you will be able to determine if the resistance of the sensor matches the temperature in the system. If it doesn’t match the radiator temperature, you probably have a faulty sensor.

On which vehicles does this problem occur most frequently

Fault code P00B7 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 (A3, Q3, Q5)
  • Chevrolet (Aveo, Cruze, Malibu, Sonic, Spark)
  • Ford
  • Nissan (Titan)
  • Opel (Astra, Corsa, Mokka)
  • Skoda (Octavia)
  • Volkswagen

Fault code P00B7 can sometimes be found with other errors. The most common are the following: P008F, P00B6, P0115, P0116, P0117, P0118, P0119, P011A, P011B.


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