⚠️A properly installed eFlexFuel kit will not trigger a Check Engine Light (CEL), Malfunction Indicator Lamp (MIL), or Service Engine Soon (SES) light after installation.
In the event a CEL/MIL/SES light appears immediately after installation, follow these steps to find the cause.
1. Retrace Your Installation
- Did you reconnect ALL hoses, lines, and connections back in? Something as simple as an unplugged vacuum hose or loose MAF sensor may trigger a fault code.
- Did you wiggle or move any hoses, lines, or connections during installation? Follow your eFlex harness and fuel lines and ensure all surrounding fittings are firmly secured.
- Did you remember to connect the ground in your eFlexFuel harness installation?
2. Did the vehicle exhibit poor operation immediately upon first startup after installation?
- If YES, review this troubleshooting guide in detail: support.eflexfuel.com/hc/en-us/articles/15875889533852
3. Determine if the vehicle is otherwise running properly
- Are there any other clues from the vehicle's operation that give you an idea of the cause?
- Any operation or drivability changes?
- Try running the Bypass Module in place of the control unit - this essentially puts your wiring back to stock. You MUST have E10 (normal gasoline) in your fuel system to use the Bypass Module.
- With the Bypass Module plugged in, try clearing the CEL/MIL/SES OBD codes.
- If the light/codes return with the bypass, your harness is either not plugged in all the way or there is an unrelated issue with the vehicle.
- If the light/codes go away with the Bypass Module plugged in, review this troubleshooting guide in detail: support.eflexfuel.com/hc/en-us/articles/15875889533852
- With the Bypass Module plugged in, try clearing the CEL/MIL/SES OBD codes.
4. Check the eFlexApp for fault codes
- Connect via Bluetooth to the eFlexApp and check for any eFlex fault codes. This may point you in the right direction to correct an installation error.
5. Pull the CEL/MIL/SES to determine the OBD fault code
With an OBD reader, pull the fault code from your vehicle. The following codes may be used for reference:
Lean Mixture - P0171, P0174 - System too lean
⚠️Engine combustion has a higher concentration of air to fuel than it should have.
Possible eFlexFuel related issues & fixes:
- The eFlexFuel Control Unit is not getting power: Double check all injector plugs and confirm the wires have a firm connection, especially the harness wire with the red wrap.
- The eFlexFuel wiring harness ground is not connected or the grounding point is corroded: Double check the harness ground wire.
- If you are able to connect to the Control Unit via Bluetooth with engine running, the power supply is okay.
Rich Mixture - P0172, P0175 - System too rich
⚠️Engine combustion has a lower concentration of air to fuel than it should have.
Possible eFlexFuel related issue & fix:
- There is an issue with connection to the ethanol sensor: Make sure the ethanol sensor is plugged in fully and firmly.
- The ethanol sensor or sensor wire is too close to high voltage components (ignition coils, leads, etc.): Move the ethanol sensor / wires further away from these high voltage components.
- Double check the eFlexApp for an ethanol sensor related fault code: If there is a related code, the ethanol sensor is likely related to the cause.
Misfires - P0300-P0312 - Random or multiple cylinder misfire
⚠️One or more cylinders are misfiring.
Possible eFlexFuel related issue & fix:
- Misfires are typically caused by problematic wiring or an issue with the eFlexFuel harness.
- Review this Troubleshooting guide in detail: support.eflexfuel.com/hc/en-us/articles/15875889533852
- Ensure all ignition related parts (spark plugs, ignition coils, leads etc.) of the engine are in good working order.
Catalytic Converter - P0420, P0421, P0422, P0430, P0431, P0432 - Catalyst system efficiency below threshold
⚠️The catalytic converter is not functioning efficiently.
Possible eFlexFuel related issue & fix:
- The eFlexFuel system does not have an effect on catalytic converter functionality.
- Lean / rich mixtures or misfiring can trigger the P0420 fault code, see these sections above.
- The catalytic converter may need replacement.
Fuel injector circuit open / circuit malfunction - P0201-P0208 - Injector Circuit Open
⚠️The vehicle ECU/ECM has detected a malfunction with one or more cylinder injector circuits.
Possible eFlexFuel related issue & fix:
- Fuel injector circuit faults can be caused by problematic wiring or an issue with the eFlexFuel harness.
- Review this Troubleshooting guide in detail: support.eflexfuel.com/hc/en-us/articles/15875889533852
- Check your injector / fueling related fuses. If a fuse is blown, try replacing with the same size. If the fuse blows again, there is a likely wiring issue.