What it means
The cylinder 4 fuel heater control circuit is reporting a low condition. The code does not establish that this is a sensor heater or affects lambda control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The cylinder 4 fuel heater control circuit belongs to the system that warms fuel for cold-weather operation. The control module monitors the circuit’s electrical condition and sets this code when it detects a low condition; that does not by itself identify a sensor heater or a fault in lambda control.
Common causes
Most likely first.
- Control line shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light
- Fuel or powertrain warning light, if equipped
- Hard starting or rough running in cold weather
- Reduced engine performance in cold conditions
How to diagnose it
- Save freeze-frame data and check whether the fault occurred during cold starting, when the cylinder 4 fuel heater may be commanded on.
- Inspect the cylinder 4 fuel heater connector and harness for corrosion, backed-out pins, chafing, or insulation worn through to ground.
- Check the connector for moisture or damaged terminals that could interfere with the cylinder 4 heater control signal.
- With the circuit safely isolated as specified by the manufacturer, check the control wire for a short to ground.
- If the wiring and connector are sound, compare the circuit readings with the manufacturer's specification and check the control module only after ruling out wiring faults.
Common fixes
- Repair chafed cylinder 4 heater control wiring and protect it from rubbing.
- Clean or repair corroded connector terminals and restore secure pin contact.
- Repair a control wire short to ground.
- Repair or replace the heater control module if circuit tests identify it as faulty.
Can I keep driving?
If the engine runs normally, a short, gentle trip may be possible, but avoid relying on the vehicle for cold starts until the fault is diagnosed. Cold-weather starting or running may worsen, and emissions may increase.
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.