What it means
The feedback line from the fuel heater control module to the ECM - reporting heater status - is open.
At a glance
- Usually lights the check-engine light
How it works
The fuel heater control module sends a feedback signal to the engine control module to report heater status. P23CD sets when that feedback circuit is open, so the engine control module cannot receive the expected status signal.
Common causes
Most likely first.
- Open or damaged feedback wiring
- Loose, corroded, or damaged connector
- Fault in the fuel heater control module feedback circuit
- Fault in the heater control module
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 fault appeared during a cold start or while the fuel heater was commanded.
- Inspect the feedback wire between the fuel heater control module and engine control module for breaks, chafing, or previous repairs.
- Check both ends of the feedback circuit for loose, corroded, wet, or pushed-back connector terminals.
- With the circuit safely isolated as specified by the manufacturer, check feedback-wire continuity end to end.
- If the wire and terminals pass continuity checks, test the module feedback circuit and fuel heater control module according to the manufacturer's procedures.
Common fixes
- Reconnect a loose feedback-circuit connector.
- Repair a broken or damaged feedback wire.
- Clean or replace corroded or damaged connector terminals.
- Replace the fuel heater control module if testing confirms its feedback output has failed.
Can I keep driving?
The main concern is hard starting or rough running in cold weather, with possible reduced performance in those conditions. If the engine starts and runs normally, short-term driving in mild weather may be possible; avoid relying on the heater until the open feedback 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.