⚠️A properly installed eFlexFuel kit will not trigger any vehicle symptoms after installation.
Symptoms with eFlexFuel Control Unit plugged in:
- Misfires, rough idle, not all injectors are firing, vehicle may not start, unusual fueling characteristics
- One or more of the following CEL/MIL/SES OBD Codes: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0309, P0310, P0311, P0312, P0316, P0320, P0321, P0322, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208
Before beginning troubleshooting, ensure all plug terminals are locked into place and the eFlexFuel harness ground is connected.
Step 1 - Running the vehicle with the Bypass Module installed & inspecting the eFlexFuel Harness
The Bypass Module is a passthrough "dummy-plug" that completes the injector wiring circuit without any signal change, mimicking stock injector wiring.
- With E10 (normal gasoline) in the tank, verified via eFlexApp if needed, install the Bypass Module in place of Control Unit. Try starting the vehicle.
→ If the vehicle demonstrates the same issues with the Bypass Module plugged in, there is an issue with the harness and the injector wiring circuit is not complete:
- This is most often caused by a loose pin/plug on the eFlexFuel harness - the wires did not clip into place during the initial install. Double check all pinned plugs to ensure connections are tight.
- This can also be caused by a damaged harness. Inspect the harness for any pinches or other signs of physical damage.
Try starting the vehicle again with the Bypass installed:
- If the vehicle still exhibits the same issues with Bypass installed, contact us.
- If the vehicle now functions without issue, try plugging the Control Unit back in and starting the vehicle.
Step 2 - Checking individual injector polarity from the main harness plug
If the vehicle functions properly with the Bypass Module installed but has issues with the Control Unit plugged in, follow the images and instructions below with vehicle turned off.
Step 3
With the vehicle off, unplug the Control Unit from the eFlexFuel harness.
Step 4
Carefully remove the orange cap from harness plug, giving you access to the pins. Use a small flathead screwdriver or pick to gently unclip the locking clips outward - repeat on both sides while gently lifting the cap.
Do not apply too much pressure or these clips may break!
Step 5
Using a multimeter in Resistance (Ω / Ohm) Mode, place the positive probe in Pin #5. Keep this probe in #5 for the remainder of the steps.
Use 20 ohm range if the meter does not have an autorange feature. Using the negative probe in Pin #5 will not work.
Step 6 – Measuring injector outputs
Place the negative probe in Pin #19. Ohm resistance should measure 10-16 Ohms.
- Repeat for Pins #20-22 (#20-24 for 6cyl application, #20-26 for 8cyl applications). All Pins should display close to the same Ohm value (+/-0.5 Ohms).
If Ohms measure close to zero for any pin (or varies significantly from the rest of the pins), then there is a wiring issue for that specific injector/plug - the polarity is likely flipped, the wire is loose in the plug, or that wire is damaged. Note which pin/injector wire has the issue.
Step 7 - Fixing the wiring issue
Follow the back of the main plug (the one you removed the orange cap from) and see what color wire this injector corresponds to, allowing you to determine which plug has an issue. Unplug the harness from that injector, carefully de-pin the corresponding plug (video below), measure continuity in your factory wiring for this injector using a multi-meter (video below), and re-pin the plug accordingly.
De-Pinning
The de-pinning process differs slightly between different plug types, but the concept remains the same. We’ve found EV6 plugs to be tricky, so we’ve created a video specific for EV6 de-pinning. If you have another plug type, you can likely still use this video for reference but know some details may differ.
Measuring Polarity
Regardless of injector type, measuring polarity is the same process. We find ChrisFix’s explanation and demonstration of how to wire the harness to be a great reference. Watch ChrisFix perform the injector wiring on his vehicle in this timestamped link:
Injector Wiring / Polarity Video: https://youtu.be/eo2jZjG1XA8?feature=shared&t=1190