Understanding the Benefits of a Flex Fuel Sensor on a 2020 Dodge Charger

Adding a flex fuel sensor to your 2020 Dodge Charger unlocks the ability to run any blend of gasoline and ethanol from E0 to E85. For Charger owners with a 3.6L Pentastar V6 or a 5.7L/6.4L HEMI V8, this upgrade not only provides fuel flexibility but can also increase horsepower and torque when using higher ethanol blends. Ethanol has a higher octane rating (around 100–105 for E85), which allows for more aggressive ignition timing and boost in forced-induction applications. Even on naturally aspirated engines, the cooling effect of ethanol can improve volumetric efficiency.

Beyond performance, flex fuel capability can be more economical when ethanol prices are low, and it reduces dependence on petroleum. For the 2020 Dodge Charger, installing a flex fuel sensor requires mechanical skill and careful wiring, but with the right guidance, it is a rewarding weekend project. This guide covers every step in detail, including safety precautions, tool selection, and post-installation tuning requirements.

Tools and Materials You Will Need

  • Flex fuel sensor kit – compatible with your Charger’s fuel line size. Popular options include GM-style sensors (e.g., Continental/GM 13577394 or 13577429) or aftermarket kits from Fuel-It! or Zeitronix.
  • Socket set – metric sockets (10mm, 13mm, 15mm) and a ratchet with extensions.
  • Wrench set – combination wrenches for fuel line fittings.
  • Pipe cutter or fuel line disconnect tool – for cutting the metal or nylon fuel line cleanly.
  • Screwdriver set – flathead and Phillips for trim removal and clamps.
  • Wire strippers, crimpers, and butt connectors – for secure electrical connections.
  • Electrical tape and heat shrink tubing – to insulate and protect wiring.
  • Safety glasses and mechanic’s gloves – fuel is toxic and flammable.
  • Fuel pressure gauge (optional) – to verify system pressure after installation.
  • Scan tool or tuning software – to calibrate the ECU to read the flex fuel sensor signal.

Safety First: Preparing Your Work Area

Fuel system work carries inherent risks. Park the Charger on a level surface, engage the parking brake, and chock the rear wheels. Work in a well-ventilated area, away from open flames, sparks, or pilot lights. Keep a fire extinguisher rated for flammable liquids nearby. Wear safety glasses and nitrile gloves to avoid skin contact with gasoline or ethanol.

Before starting, relieve fuel system pressure. Locate the fuel pump fuse in the underhood fuse box (usually the “Fuel Pump” or “FP” fuse). Start the engine and let it idle until it stalls from fuel starvation. Then disconnect the battery’s negative terminal. This prevents accidental sparks and protects the ECU during wiring.

Locating the Fuel Line and Sensor Mounting Position

The 2020 Dodge Charger has the fuel line running along the driver-side frame rail from the fuel tank to the engine. The ideal location for the flex fuel sensor is on the high-pressure side of the fuel system, after the fuel filter but before the engine fuel rail. On the Charger, a common mounting point is near the driver-side strut tower or along the frame rail where the nylon fuel line is accessible.

If you have a 3.6L Pentastar, the fuel line is a plastic (nylon) line with quick-connect fittings. For the 5.7L or 6.4L HEMI, the line is metal (steel) from the tank to the engine. In both cases, you will need to cut the line and insert the sensor using appropriate fittings (compression fittings or push-to-connect adapters). Many flex fuel sensor kits include adapters for 3/8″ or 5/16″ line, but verify your Charger’s specific line diameter.

Select a location where the sensor is away from exhaust heat, moving parts, and potential road debris. Use the provided bracket to secure the sensor to a solid chassis point. Ensure the sensor’s electrical connector is oriented upward to prevent moisture ingress.

Step-by-Step Installation Process

Step 1: Disconnect the Battery

With the engine off and pressure relieved, disconnect the negative battery terminal. Use a 10mm socket to loosen the terminal clamp, then tuck the cable aside where it cannot touch the battery post. Wait at least five minutes for any residual voltage in the ECU capacitors to dissipate.

Step 2: Access the Fuel Line

Depending on your engine, you may need to remove the engine cover and some intake ducting. For the 3.6L, remove the plastic engine cover by pulling upward. For the 5.7L, loosen the air intake tube at the throttle body to gain clearance. Use a socket to remove any brackets blocking access to the fuel line.

If your Charger has underbody shielding, you may also need to remove the plastic belly pan under the driver side. Use a flathead screwdriver to pry out the push-pins or a 7mm socket to remove bolts.

Step 3: Cut the Fuel Line

For nylon lines: Use a plastic fuel line cutter or a razor knife to make a square, clean cut. Do not use a saw or hacksaw—plastic shavings can contaminate the fuel system. For metal lines, use a mini pipe cutter designed for brake lines or fuel lines. Rotate the cutter around the line to score it evenly, then snap the line cleanly. Place a rag under the cut area to catch any residual fuel.

Measure the length of the sensor body (usually about 3–4 inches) plus the fittings. Mark the line and cut it such that the sensor will be centered in the gap. Double-check alignment before cutting.

Step 4: Install the Flex Fuel Sensor

Deburr the cut ends of the fuel line with a file or emery cloth to remove sharp edges. Attach the supplied fittings to each end of the sensor. For compression fittings, slide the nut and ferrule over the line, then insert the line into the sensor port and tighten the nut to the manufacturer’s torque specification (typically 15–20 ft-lb). For push-to-connect fittings, press the line in firmly until it clicks. Gently tug to confirm engagement.

Position the sensor in the bracket and mount it to the chassis using the provided bolts. Ensure the sensor is not strained or kinked. Tighten all clamps and fittings securely. Wipe away any fuel spills.

Step 5: Connect the Wiring to the Vehicle

The flex fuel sensor typically has three wires: a 5V reference, a ground, and a signal output. On GM-style sensors, the pinout is:

  • Pin A – Ground (black)
  • Pin B – Signal output to ECU (blue or white)
  • Pin C – 5V reference voltage (purple or red)

You will need to tap into the engine control module (ECM) wiring or use a standalone flex fuel controller. If your Charger has an aftermarket ECU or custom tune, you can directly connect the sensor to an analog input. For stock ECUs, you must use a flex fuel compatible tune (e.g., from HP Tuners or a custom tuner) that can interpret the sensor’s frequency output. Some tuners provide a wiring harness that piggybacks into the existing fuel injector or MAP sensor wiring.

Route the sensor wires away from hot components and sharp edges. Use wire strippers to expose about 1/4 inch of copper on each wire. Connect to the corresponding vehicle wires using butt connectors or solder and heat shrink. Wrap the connections with electrical tape to prevent moisture shorting. Secure the wire loom with zip ties.

Step 6: Reconnect the Battery and Check for Leaks

Reattach the negative battery terminal and tighten securely. Before starting the engine, prime the fuel system by cycling the key to the “ON” position (engine off) three times, each time waiting for the fuel pump to stop. This pressurizes the system. Inspect all fuel line connections for leaks. You may use a mirror to see underneath the sensor. If you see any fuel weeping, tighten the fittings slightly.

Step 7: Test the Installation and Calibration

Start the engine. It may take a few seconds to build fuel pressure. Listen for any unusual noises. With the engine idling, check the sensor data using a scan tool or tuning software. The ethanol content reading should be close to the actual fuel in your tank (e.g., if you have E10, the reading should be around 10–15%). Monitor the fuel pressure to ensure it stays within normal range (typically 55–58 psi for returnless systems).

Take a short test drive, monitoring for any hesitation or performance changes. If the vehicle runs poorly, the sensor may be incorrectly wired or the tune may not be calibrated. Contact your tuner for adjustments. Once everything is verified, reinstall any removed trim, intake ducting, and the engine cover.

Post-Installation Tuning and ECU Calibration

A flex fuel sensor alone does not change engine behavior—the ECU must be programmed to read the sensor and adjust fuel timing and injection accordingly. For 2020 Dodge Chargers, this requires custom tuning via software like HP Tuners or DiabloSport Predator/Trinity. Many performance shops offer flex fuel tuning packages for the 3.6L and HEMI engines. If you are not comfortable with tuning, hire a professional.

The tuner will calibrate the ECU to use the sensor’s frequency signal (typically 50–150 Hz corresponding to 0–100% ethanol) to calculate the stoichiometric air-fuel ratio. For example, E85 requires a richer mixture (around 9.7:1) compared to gasoline (14.7:1). The sensor also detects fuel temperature, which the ECU can use for more accurate fueling.

Expect a noticeable power increase on high ethanol blends—up to 20-30 horsepower on a naturally aspirated HEMI, and even more on supercharged applications. The ethanol’s cooling effect reduces knock, allowing more ignition advance.

Common Pitfalls and How to Avoid Them

  • Using the wrong sensor orientation: Some sensors are flow-direction sensitive. Check the manufacturer’s arrow direction. Incorrect flow can cause erratic readings.
  • Inadequate fuel line support: If the sensor is not securely bracketed, vibrations can loosen fittings over time. Use a bracket that mounts to a solid chassis point.
  • Poor wiring connections: Loose or corroded connections cause signal loss. Always solder or use quality crimp connectors and apply heat shrink.
  • Skipping fuel pressure relief: Failure to relieve pressure can result in high-pressure fuel spray during line cutting—dangerous and messy.
  • Not updating the tune: Running a flex fuel sensor without a compatible tune will result in the engine ignoring the sensor, or worse, running lean and causing damage.

Maintenance and Longevity

Modern flex fuel sensors are durable, but ethanol can attract moisture over time. Periodically inspect the sensor for leaks and check that the electrical connector is clean and dry. If you frequently switch between gasoline and E85, the sensor may accumulate deposits—running a tank of premium gasoline every few thousand miles can help clean the system. Most sensors last over 100,000 miles with proper care.

For the 2020 Dodge Charger, the fuel system is designed to handle ethanol blends up to E15 for stock vehicles. When retrofitting for E85, replace the fuel pump and injectors if they are not ethanol-rated. The stock pump on the 3.6L and 5.7L is usually sufficient for E85 up to moderate power levels (500-600 hp), but for higher output, an upgraded pump is recommended.

Conclusion

Installing a flex fuel sensor on your 2020 Dodge Charger opens the door to cheaper fuel options and significant performance gains. By following this guide and working carefully with the fuel system, you can complete the mechanical installation in an afternoon. The key to success is pairing the sensor with a proper ECU tune. Whether you drive a V6 or HEMI, flex fuel capability makes your Charger more versatile and enjoyable.

For additional information, refer to the user manual for your specific flex fuel sensor kit and consult with a Dodge tuning specialist. You can also learn more about ethanol’s benefits from the Renewable Fuels Association.