This ChrisFix video does an amazing job detailing each step of the Toyota Prius installation. We highly recommend referencing this video while using the main Installation and User Guide included with your kit. The main Installation and User Guide can also be accessed here: https://eflexfuel.com/pub/media/ladattavat/eflexfuel-manual-auto-us.pdf
If you attempt installation and run into any roadblocks, do not hesitate to reach out so we can help solve the issue. With over 60,000 installations worldwide, we are here to help ensure your vehicle runs seamlessly on gasoline, E85, or any blend of the two with eFlexFuel installed.
See below supplementary tips to help complete your installation
Kit components include:
- eFlexFuel Control Unit: The eFlexFuel “brains” / ECU.
- Engine specific harness: Wiring harness to connect this kit to your vehicle.
- Engine specific fuel line accessories: Fuel line components to install the Ethanol sensor.
- Ethanol Content Sensor: Measures Ethanol % of fuel.
- Bypass Module: A “dummy plug” that can be used in place of your eFlexFuel Control Unit for troubleshooting, NOT an OBD plug. Normal gas (E10) must be in the tank to use the Bypass Module. See the Customer Support Center for more information.
YOU WILL BE DICONNECTING FUEL LINE DURING THIS INSTALLATION – ALLOW THE ENGINE AND COMPONENTS TO FULLY COOL DOWN BEFORE ATTEMPTING INSTALLATION.
1. Pre-Installation
Read all steps and plan for this installation. Not following instructions may lead to a temporarily inoperable vehicle. Review full instructions before beginning and do not skip any steps.
2. Ethanol Sensor Installation
Always use hose clamps where rubber hose is used and quick connectors on all connections.
- The sensor can mount facing either direction as it has no flow direction.
- The ethanol sensor and sensor wire should be as far as possible from the coils and ignition leads to prevent electrical interference.
- Check that connections are properly tightened. You can prime the fuel pump to look for leaks.
3. Preparing the Wiring Harness
Unplug the OEM wiring harness from the injectors. Be careful not to use too much force on the retaining clip as old plastic can be brittle.
Measuring Fuel Injector Polarities
- This step is crucial! Carefully follow the instructions in the main installation guide and watch this ChrisFix video for further detailed instruction: https://youtu.be/eo2jZjG1XA8?feature=shared&t=1190
- Take your time on this step! An error here will lead to malfunction when you first start the vehicle and can be tedious to correct as you will need to de-pin.
- If you run into issues on this step and polarity may be flipped, visit our Customer Support Center for how to test & de-pin.
Connecting the Male Connectors to the eFlexFuel Wiring Harness
- Connector pins/terminals may go in both ways but will only lock if inserted in the correct orientation.
- Confirm the pins are locked into place by gently pulling the wire for resistance.
4. Wiring Harness Installation
Placing the Temperature Sensor
- Zip tie or fasten the end of the temp sensor as close to the engine block as possible, such as under one of the fuel rails.
- The purpose of the temp sensor is only to communicate appx engine temperature during startup (e.g. a cold engine on cold start Vs a warmed up engine starting on a cold day).
- The temp sensor enables the eFlex Control Unit to properly calibrate startup fueling but has no effect on regular operation.
Connecting the Ground Wire
- We recommend using the engine block as your main ground, though other primary grounds can also work.
- Do not use a grounding point near ignition components or their leads.
- Good grounding is necessary for proper eFlexFuel functionality. If the device does not turn on or you have Bluetooth issues, and injector polarity is correct, re-check the ground.
Installing the Control Unit
- Find a dry place for the control unit and secure it with an appropriate bolt, zip-ties, high strength double sided tape, or velcro.
- It is important not to put strain on the main connector to the Control Unit. Confirm there is some play/slack when plugging in.
Connecting the Optional eFlexPro 0-5V Analog Input Sensor Wire(s)
- The eFlexPro kit comes with one analog input wire already installed in your harness. This wire is optional and typically only connected to an aftermarket wideband. If unused, simply wrap this wire up neatly.
- This wire has zero impact on the eFlexPro’s performance and is only used for optional datalogging for tuning purposes. For more information on the optional 0-5V Analog Input Sensor Wire(s), please visit the Customer Support Center.
Securing the Wiring Harness
- Any unused length of the harness should be bundled and run alongside the fuel rail. Zip tie this in place.
- When both bundles reach the firewall, you can combine them into one, running to the Control Unit.
- Make sure any slack is safely secured so there is no risk of touching moving or hot parts.
- Check surrounding components that only move sometimes, such as windshield wipers, steering components, etc.
- Due to the nature of electrical components, a clean install also has a positive effect on the signal strength and minimizes electrical interference.
Still have questions? We are here to help!
- First, try visiting the Customer Support Center at support.eflexfuel.com and searching and/or browsing our troubleshooting guides. Most answers are there!
- Email us at support@eflexfuel.com
- Call us Mon-Fri between 9AM-5PM PT at 833-539-3835
Thank you for joining the #E85Movement!
We hope you make the most of your additional torque and horsepower. We invite you to follow us on Facebook (eFlexFuelUSA) and Instagram (@eflexfuel) to join a community of likeminded individuals. Most importantly, have fun and enjoy your drive!