What it means
The cylinder 1 fuel heater has a performance fault: it is not operating as expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The cylinder 1 fuel heater is intended to support fuel heating under the conditions specified by the vehicle's control system. P23D4 sets when the heater's operation does not meet the expected performance, which may reflect a weak heater element, poor connection, wiring resistance, or a control-module problem.
Common causes
Most likely first.
- Cylinder 1 fuel heater element worn or damaged
- Open or high resistance in heater wiring or connector
- Fault in the heater control module
- Poor electrical connection or ground
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
- Review freeze-frame data and note the temperature and heater command when the cylinder 1 performance fault was recorded.
- Inspect the cylinder 1 heater, its connector, and wiring for damage, corrosion, looseness, or signs of overheating.
- Check the heater circuit's power and ground connections while the cylinder 1 heater is commanded, following the manufacturer's procedure.
- Measure the cylinder 1 heater element and circuit for continuity or excessive resistance against the manufacturer's specification.
- If the heater and wiring pass, verify the control-module command and output using the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure a poor cylinder 1 heater connection or ground.
- Repair high-resistance or damaged wiring in the cylinder 1 heater circuit.
- Replace the cylinder 1 fuel heater if its element fails testing.
- Replace the heater control module only if its output is faulty after the heater and circuit are verified.
Can I keep driving?
The performance fault may cause hard starting, rough running, or reduced engine performance in cold weather. If the engine runs normally in mild conditions, driving may be possible, but arrange repair before relying on the vehicle in freezing temperatures.
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.