What it means
The cylinder 4 alternative-fuel injector control circuit has a voltage below the expected range. This indicates an electrical circuit fault, not necessarily an injector flow problem or short to ground.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
In a bi-fuel vehicle, the alternative-fuel injector for cylinder 4 is controlled by an electrical drive circuit separate from the petrol or diesel injector. The control module sets this code when the cylinder 4 circuit voltage falls below its expected range, which points to an electrical fault and does not by itself prove that the injector is blocked or shorted to ground.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Misfire or rough idle on the affected cylinder
- Increased fuel consumption
- Possible fuel smell or smoke from exhaust
How to diagnose it
- Review freeze-frame data and live misfire counts to see whether the low reading coincides with alternative-fuel operation and a cylinder 4 misfire.
- Inspect the cylinder 4 alternative-fuel injector connector and harness for corrosion, chafing, damaged insulation, loose terminals, or contact with engine ground.
- Check the injector's supply and control wiring for a short to ground, following the manufacturer's circuit isolation procedure.
- Measure voltage and continuity at the cylinder 4 injector connector and compare readings with the manufacturer's specification to locate excessive resistance or a grounded wire.
- If the harness and connector check out, test the injector and control-module driver circuit using the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure corroded or loose cylinder 4 injector connector terminals; replace damaged terminals as needed.
- Repair chafed cylinder 4 injector wiring and restore its insulation and routing.
- Replace the cylinder 4 alternative-fuel injector if it fails the manufacturer's electrical checks.
- Repair or replace the control module if its cylinder 4 driver is confirmed faulty.
Can I keep driving?
Avoid using the alternative-fuel mode while cylinder 4 misfires; switch fuel modes only if the vehicle runs smoothly and the manufacturer allows it. A continuing misfire can raise emissions and damage the catalytic converter; stop if fuel odour or exhaust smoke appears.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.