What it means
A fault has been detected in the cylinder 1 fuel heater control circuit. The code does not establish a particular engine type or heater purpose.
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 control circuit is the electrical path used to control the heater assigned to cylinder 1. P23D1 sets when that circuit is open, so the commanded heater circuit lacks electrical continuity.
Common causes
Most likely first.
- Open in heater or wiring
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
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
- Record freeze-frame data and check whether the open-circuit fault appeared during cold operation or a cylinder 1 heater command.
- Locate the cylinder 1 fuel heater using the vehicle's service information and inspect its connector and wiring for damage or a pin pushed back into the housing.
- Check the cylinder 1 heater connector and related module connectors for corrosion, looseness, or moisture.
- With power isolated as directed by the manufacturer, check continuity through the cylinder 1 heater circuit and its wiring.
- If the harness is intact, test the cylinder 1 heater and control-module output using the manufacturer's procedures.
Common fixes
- Seat a pushed-back or loose terminal in the cylinder 1 heater connector.
- Repair an open or damaged wire in the cylinder 1 heater circuit.
- Replace a damaged connector or repair a confirmed cracked connection in the module.
- Replace the cylinder 1 fuel heater or control module only if testing identifies it as the source of the open.
Can I keep driving?
A failed cylinder 1 heater circuit can cause hard starting, rough running, or reduced performance in cold weather. If the engine runs normally in mild conditions, driving may be possible, but avoid relying on it for cold starts until the open circuit is repaired.
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.