What it means
The cylinder 1 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 1 fuel heater control circuit carries the control signal for the heater assigned to cylinder 1. P23D3 sets when the control module detects a low electrical condition on this circuit, which can occur if the control line is shorted to ground.
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
- Record freeze-frame data and check whether the low condition appeared during cold operation or a cylinder 1 heater command.
- Inspect the cylinder 1 heater control wire for chafing or contact with grounded metal.
- Check the cylinder 1 heater and control-module connectors for corrosion, moisture, loose pins, or terminals pushed back into the housing.
- Compare the live cylinder 1 control reading with the heater command and see whether the signal remains low.
- Test the control wire for an unintended path to ground and check circuit continuity against the manufacturer's specification.
Common fixes
- Repair cylinder 1 control wiring that is chafed through and contacting ground.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace a damaged connector or harness section.
- Replace the cylinder 1 heater or control module only if circuit tests identify it as faulty.
Can I keep driving?
A low control signal can leave the cylinder 1 fuel heater unable to operate correctly, causing hard starting or rough running in cold weather. Avoid relying on the vehicle in freezing conditions until the grounded or low-resistance circuit fault is fixed.
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.