What it means
The cylinder 1 fuel heater control circuit is reporting a high 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 1 fuel heater control circuit carries the control signal for the heater assigned to cylinder 1. P23D2 sets when the control module detects a high electrical condition on this circuit, which can result from the control line contacting a supply voltage.
Common causes
Most likely first.
- Control line shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 high condition appeared during cold operation or a cylinder 1 heater command.
- Inspect the cylinder 1 heater control wire for pinched insulation or contact with a powered wire or terminal.
- Check the cylinder 1 heater and control-module connectors for corrosion, loose pins, or terminals pushed back into the housing.
- Compare the live cylinder 1 control reading with the commanded heater state to see whether the signal stays high.
- Test the control wire for an unintended connection to a supply circuit, using the manufacturer's wiring information.
Common fixes
- Repair the cylinder 1 control wire where it is pinched against a power source.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace a damaged connector or harness section that lets the control line contact supply voltage.
- Replace the cylinder 1 heater or control module only if circuit tests confirm the component is faulty.
Can I keep driving?
The cylinder 1 heater may not operate as intended, which can make cold starts or cold-weather running difficult. If the engine runs normally in mild weather, short-term driving may be possible; avoid relying on it in freezing conditions until the high condition 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.