Fault code P008F is called “Engine Coolant Temperature (ECT)/Fuel Temperature (FT) 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 P008F
When the OBD-II code P008F appears on your vehicle, it means that the Powertrain Control Module (PCM) has detected a mismatch in the correlated signals. Inconsistency between perceived engine coolant temperature (ECT) and fuel temperature.
ECT sensors consist of a thermistor immersed in solid resin and housed in a metal or plastic housing. The ECT housing is designed so that it can be screwed into a coolant channel in the engine intake manifold, cylinder head, or block.
When warm coolant flows through the passages and through the ECT sensor, the thermal resistance level is reduced. When the engine coolant temperature drops, the resistance increases, and as a result, the voltage of the ECT sensor circuit decreases.
These resistance fluctuations are interpreted by the PCM as changes in engine coolant temperature. The ECT sensor inputs are critical in calculating the fuel delivery and ignition advance strategy.
The fuel temperature sensor also uses a thermistor, but it is low voltage. Fuel temperature can be especially important to the driveability of vehicles that use a diesel engine.
Engine coolant temperature and fuel temperature are usually only correlated when the engine is at ambient temperature.
Code P008F will be stored and the Malfunction Indicator Light (MIL) may illuminate if the PCM detects a mismatch between the ECT sensor and the fuel temperature sensor. Which varies by more than the maximum allowable parameters over a set period of time and under certain circumstances.
Symptoms of vehicle malfunctions
The main signal that an error P008F has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a fault).
- Reduced engine power.
- Increased fuel consumption.
- Black smoke coming out of the exhaust pipe, when running on rich mixture.
Stored code P008F is of medium severity. Since ECT and fuel temperature are important for proper fuel strategy and ignition timing.
Factors that can cause this error code
The error code P008F can mean that one or more of the following problems have occurred:
- ECT sensor has failed.
- Defective fuel temperature sensor.
- Coolant or fuel temperature sensor circuit is broken.
- The wiring harness or connector for the coolant temperature or fuel sensor is damaged.
- Sometimes faulty PCM is the cause.
How to fix or reset OBD-2 code P008F
Some suggested steps for troubleshooting and fix the error code P008F:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P008F appeared.
- Clear the error codes from the computer memory and test-drive the vehicle to find out if the error appears again.
- Visually inspect the electrical wires and connections related to the sensors for looseness and damage. Correct the problem if necessary.
- If the ECT or fuel temperature sensor has failed, replace it.
- 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 error P008F, 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 the coolant temperature sensor (ECT)
Visually inspect the sensor for damage to the wiring or connector, and repair if necessary. Then connect the 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 temperatures around -70°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 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 P008F can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- BMW (X3, X5)
- Chevrolet
- Ford (Mondeo)
- GMC (Sierra)
- Mercedes-Benz (Sprinter)
- Renault
Fault code P008F can sometimes be found with other errors. The most common are the following: P00B6, P00B7.
