We have encountered technical software problems in firmware version 6.0. If your car does not work properly or the engine fault codes light up, please contact our support. You can find the contact info on this page from the last tab.

This problem may not apply to your car, even though the device version is mentioned above.

Attention when installing wiring harness!

Fault situations

  • eFlexFuel is installed to used vehicles in which components or component properties may have been changed from the original. For this reason, there may be situations where the product is suitable for 99 % of identical cars, but not suitable for 1 %. For example, over-worn parts of the ignition and fuel supply may interfere with the operation of the device so that it does not function in the intended manner.
  • Below we have listed a variety of cases where using ethanol has caused engine malfunctions and possible solutions for these problems. These malfunctions are usually due to defective or worn components of the vehicle or by mistakes in installation.
  • Car is running lean or too rich and shuts off
    • The spark plugs were replaced
  • Misfiring in cylinders
    • The spark plugs were replaced
    • The fuel injectors were cleaned
    • The fuel injectors were replaced
  • eFlexFuel stutters
    • The spark plugs were replaced
    • Broken ignition coil was replaced
    • Male connectors of wiring harness were poorly connected
    • Ground wire was poorly connected
  • Check engine fault codes of Lambda
    • Lambda sensors were replaced
  • Poor cold start
    • The spark plugs were replaced
    • Car battery was replaced
  • Too lean with ethanol and after also with gasoline
    • Fuel filter was stuck and was replaced
    • Fuel pump was broken and was replaced
  • Check engine fault code of catalytic converter
    • Catalytic converter was replaced
  • eFlexFuel fault code from ethanol sensor
    • Ethanol sensor connector was poorly connected
  • In some cars, the on-board computer and fuel consumption screen are based on computational consumption. As a result, the display of the on-board computer and the fuel consumption screen can deviate from the reality with E85.

Bluetooth and eFlexFuel App

  • The newest PCB5.0+ version devices come without a PIN-code.
  • The pin code can be found on the nameplate behind the control unit. It is: 8585 (PCB4.2) or 858585 (PCB4.3+).
  • Check the control unit nameplate for PCB version
  • PCB4.2 and older: To store
  • PCB4.3+: To store
  • Some Bluetooth devices with Bluetooth or Bluetooth Low Energy technology do not support eFlexFuel. Android operating systems are used in thousands of different Bluetooth chip combinations, so it's virtually impossible to guarantee 100% compatibility.
  • We are constantly working to provide our customers with the widest possible compatibility with our devices. Our apps are updated every 1-2 months.
  • Make sure that your mobile device does not have Bluetooth power saving features on!
  • Some car structures hinder radio traffic in the car's interior.
  • Some mobile devices have a poor connection with Bluetooth devices.
  • Mobile device covers can weaken the Bluetooth signal.
  • Your mobile device does not see the eFlexFuel device in the Bluetooth device list.
    • The mobile device sees only MAC address devices. The eFlexFuel name changes when the device is paired.
  • eFlexFuel App shuts down during usage
    • Car structures and radio signals can disconnect the Bluetooth connection.
    • The problem may be in the application's operation and not in the Bluetooth connection. You can report a bug to
  • The eFlexFuel control unit can not be connected even if the pairing is done.
    • Make sure your eFlexFuel is turned on by starting the engine.
    • Make sure you have granted Bluetooth permissions to the eFlexFuel App.
    • Try pairing the devices again.
    • Try unplugging the eFlexFuel from the wiring harness and plug it again.
    • Try connecting with a different mobile device.
    • Try connecting the engine compartment open.
  • The eFlexFuel can not be paired even if the device is displayed on the Bluetooth device list.
    • Make sure your PIN is correct.
    • Try pairing the device via eFlexFuel App.
    • Make sure your eFlexFuel is turned on by starting the engine.
    • Try unplugging the eFlexFuel from the wiring harness and plug it again.
    • Try connecting with a different mobile device.
    • Try connecting the engine compartment open.
  • Ethanol sensor not connected
    • Check that the ethanol sensor connector is properly attached and wire is not damaged.
  • Low ethanol content
    • Ethanol sensor has detected low ethanol content. Warning limit is 2 %. Normally gasoline contains 5 % or more ethanol. Low ethanol content could show symptoms of low fuel pressure or a faulty connected ethanol sensor.
  • Fuel is contaminated
    • Ethanol sensor has detected dirty gasoline or water in the fuel. If the sensor cannot detect right ethanol content, the ethanol content is set to 40 % for safety reasons. In this case, avoid driving or refuel about 50/50 mixture of gasoline and ethanol.
  • Temperature sensor signal is too low
    • Temperature sensor is faulty or wire is damaged.
  • Temperature sensor signal is too high
    • Temperature sensor is faulty or wire is damaged.
  • Duty cycle warning
    • Injector duty cycle has reached 100 %. Follow the duty cycle level while driving. If the duty cycle goes to 100 % in hard accelerations, we recommend using few liters of gasoline per tank with E85. The reason may be clogged fuel nozzles, fuel filter, faulty fuel pump, or inadequate fuel system for E85.
    • If ethanol content percent is 0% check that you have installed ethanol sensor to fuel line.

Car running badly

  • Ethanol is less flammable than gasoline, so the ignition problems can occur more easily when using ethanol. In some cars, a slight jerking during the first 5 minutes of driving is normal in cold weather conditions.
  • If the spark plugs or ignition coils are defective or have reached full lifetime, small jerking can occur with a cold engine.
  • Solution
  • We recommend that the engine be preheated with cold weather conditions. Also when using gasoline.
  • Add a few liters of petrol to the tank.
  • Replace worn ignition components.
  • Check engine light can be on for many different reasons. If the check engine light came on after installing eFlexFuel, there is a reason to suspect that the device is not properly installed.
  • Solution
  • The first check the error code
    • If the problem is related to ignition, there is a reason to suspect that the wiring harness is connected incorrectly or badly.
  • Check for eFlexFuel fault codes with the eFlexFuel App.
    • Check the ethanol content to show the correct ethanol content.
    • Check the temperatures see that there are correct.
  • Check the eFlexFuel wiring harness
    • Make sure that the ground wire is properly connected. Car battery (-) is the best place for a ground wire.
    • Make sure that each connector on the cylinder and the terminals are properly connected.
    • Make sure that the male connectors on the cylinders are correctly with their polarities (multimeter part in the instruction manual).
  • Check that the eFlexFuel connector pins are straight.
  • The eFlexFuel control unit has failed and needs to be replaced.
  • Ethanol is less flammable than gasoline, so the car may not always start on the first attempt.
  • Normally the car will start with 1 to 3 starts even in cold weather.
  • If the spark plugs or ignition coils are defective or reach full lifetime, start up may require a few extra tries.
  • Solution
  • eFlexFuel automatically learns from poor starts based on ethanol content and temperature sensor readings.
  • We recommend that the engine is preheated before a cold start. Also when using gasoline.
  • Add a few liters of petrol to the tank.
  • Replace worn ignition coils.
  • If the defect in the car lights up with pure ethanol, there is reason to suspect that the car's nozzles do not produce enough fuel for the engine.
    • Check that the ethanol content looks right with the eFlexFuel App.
    • Add gasoline to the tank. If the car starts to run normally with the addition of gas, then eFlexFuel works correctly.
  • Solution
  • The fuel filter may be clogged.
  • Clean the fuel injectors.
  • The fuel pump may be malfunctioning.
  • Fuel injectors capacity may be too small for the use of pure E85.
    • We check each eFlexFuel compatible car. We always inform the customer if the fuel injector capacity is too small for the E85.

Contact support

  • Contact email: help(at)
  • Tell us why do you want to return eFlexFuel.
  • Take a picture if you suspect that you have gotten a faulty product.
  • We send the return documents via email.
  • See all the support content once more.
  • If you bought a device installed from the installation point, contact your installer first.
  • Contact email support(at) Mention in the message:
    • What device version do you have (back panel of the control unit)
    • Vehicle information
    • Tell us about the fault situation as accurately as possible
  • We try to respond to the messages as soon as possible on weekdays.

Check the compatibility for your vehicle

eFlexFuel is not available for direct injection engines (CGI, FSI, GDI, EcoBoost, etc.) or diesel engines.

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If you cannot find your vehicle you can leave us a compatibility request. We add vehicles to our database when we are asked for compatibility.

a) VIN code is 17 characters. b) i, o, q are not allowed.

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