Attention when installing wiring harness!

  • eFlexFuel cost 349 € including shipping and accessories. Shipments to outside EU are tax free (-24 % finnish VAT.).
  • We always supply products that fits in the car based on its technical information. If you think you have received the wrong products, please contact us.
  • PCB4.2 version the PIN-code is 8585.
  • PCB4.3 version the PIN code is 858585.
  • PCB5.0+ versions are without PIN code.
  • In some cars the signal is too weak to the cabin.
  • The signal strength is weak in some mobile phones.
  • Some mobile devices have a poor connection with Bluetooth devices that can affect the signal.
  • Mobile device protective cover may weaken the bluetooth signal
  • Mobile device does not see the eFlexFuel device on the Bluetooth device list.
    • The mobile device can not be seen in the MAC list. The name of eFlexFuel may only change after the device is paired.
  • eFlexFuel App shuts down during usage
    • The problem is probably in the application's operation and not in the Bluetooth connection. You can report a bug to
  • The eFlexFuel device can not be connected even if the pairing is done.
    • Make sure your eFlexFuel is turned on by turning engine on.
    • Make sure you have granted all the permissions to the eFlexFuel App.
    • Try pairing the device again.
    • Try unplugging the eFlexFuel from the harness and plug it again.
    • Try connecting with a different mobile device.
    • Try connecting the hood open.
  • eFlexFuel has a fault code
  • Fault codes
  • Ethanol sensor not connected
    • Check the connector that it is properly connected.
  • Low ethanol content
    • Ethanol sensor has read low ethanol content. Warning area is under 2 %. Normally gasoline includes 5 % or more ethanol. Low ethanol content could show symptoms of low fuel pressure or faulty connected ethanol sensor.
  • Fuel is contaminated
    • Ethanol sensor has detected dirty gasoline or water in fuel. Is sensor cannot detect right ethanol content, for safety reason the ethanol content is set to 40 %. In this case, avoid driving or refueling about 50/50 of gasoline and ethanol.
  • Temperature sensor signal is too low
    • Temperature sensor is faulty.
  • Temperature sensor signal is too high
    • Temperature sensor is faulty.
  • Duty cycle warning
    • Duty cycle has reached to 100%.
  • Ethanol is less flammable than gasoline, so the ignition problems can occur more easily when using ethanol. In some cars a slight hickups during the first 5 minutes of driving is normal in cold weather conditions.
  • If the spark plugs or ignition coils are defective or reach full lifetime, smlight hickups can occur with a cold engine.
  • Solution
  • We recommend that the engine is preheated with cold weathers also when using gasoline.
  • Add a few liters of gasoline to the tank.
  • Replace spark plugs or ignition coils.
  • Vehicles fault codes can ignite for many different reasons. If the fault code light came on after installing eFlexFuel, there is a reason to suspect that the device is not properly installed.
  • Solution
  • Check the fault code.
    • If the problem is related to ignition, there is a reason to suspect that the wiring harness is connected incorrectly or poorly.
  • Check with eFlexFuel App for eFlexFuel fault codes.
    • Check the ethanol content it shows correct concentration.
    • Check the temperature to see that is is correct.
  • Check the wiring harness.
    • Make sure the ground wire is connected properly. Battery ground is the best place for ground wire.
    • Make sure each connector on the fuel injector and the connector terminal are properly connected.
    • Make sure the polarity with male connectors are correct with multimeter.
  • Check the strip connectors terminal pins are straight.
  • eFlexFuel control unit could be faulty and it should be replaced.
  • Ethanol is less flammable than gasoline so the vehicle may not always start with the first time.
  • Normally the car will start at 1 to 3 start ups even in cold weathers.
  • If the spark plugs or ignition coils are defective or reach their full life, start-up may require a few companies.
  • Also poor battery will affect cold starting.
  • Solution
  • eFlexFuel learns from bad starts and fixes cold enrichments automaticully.
  • We recommend that the engine is preheated with cold weathers also when using gasoline.
  • Add a few liters of gasoline to the tank.
  • Replace spark plugs or ignition coils.
  • If fault codes ignites only with ethanol there is a reason to suspect the fuel pump do not produce enough fuel to the engine
    • Check the ethanol content is correct with eFlexFuel App
    • If the car starts to run normally with the addition of gasoline, then eFlexFuel will work properly.
  • Solution
  • The fuel filter may be clogged.
  • Clean fuel injectors.
  • Cloggage in fuel lines.
  • Fuel pump may be faulty.
  • Fuel injectors could be too small for using ethanol
    • We always check vehicles compatibility before shipping the eFlexFuel to customers. We always inform the customer if the fuel injectors could be too small for using ethanol.
  • See all the support content once more.
  • If you purchased the device installed from the installation point, contact your installer first.
  • If you bought eFlexFuel from this site contact help(at) Please include to email:
    • What device version do you have (back panel of the control unit)
    • Vehicle information
    • Tell as accurate as possible about the fault situation
  • We try to respond to the messages as soon as possible on weekdays.

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Check the compatibility for your vehicle

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

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Not compatible to following engines:

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  • Manufacturer
  • StepOne Tech Ltd
  • Myllyhaantie 7
  • 33960 Pirkkala
  • Finland
  • FI24890300

eFlexFuel™ is developed and made in Finland

eFlexFuel™ is trademark owned by StepOne Tech Ltd