P23D5

Code

Generic P — Powertrain

Cylinder 2 Fuel Heater Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 32 RU: 21

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Page language: EN

Causes

Open or damaged wiring harness to Cylinder 2 fuel heater
Corroded, loose, or damaged connector at the injector or ECM
Failed/heated element in the Cylinder 2 injector/fuel heater
Blown fuse or faulty relay supplying the heater circuit
Poor or intermittent ground connection
Faulty ECM driver output (rare)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Cold-start difficulty or extended cranking (if heater used for cold conditions)
Possible rough idle or reduced engine performance in cold conditions
No immediate driveability symptoms in warm conditions; fault stored

What to check

Use a scan tool to read freeze-frame data, readiness and live data for fuel heater command and status
Visually inspect wiring and connectors at Cylinder 2 injector for damage, corrosion or disconnection
Back-probe the heater connector while commanding heater ON to verify voltage and ground
Measure resistance of the Cylinder 2 heater element (with battery disconnected)
Check fuses/relays related to the fuel heater circuit
Inspect engine ground straps and power distribution for proper connections

Signal parameters

Expected supply voltage to heater circuit when commanded: approximately 11–13.5 V (varies by vehicle)
Expected heater element resistance (typical range): about 0.2–10 ohms (refer to OEM spec) — low-ohm load
Open/high-resistance condition: infinite or much higher than manufacturer spec
Current draw when heater energized: usually 0.5–5 A depending on design
ECM command may be a switched 12 V or a low-side driver to ground; verify with vehicle wiring diagram

Diagnostic algorithm

Connect a professional scan tool. Read and record DTC(s), freeze-frame and live data. Note whether ECM is commanding the Cylinder 2 heater.
Visually inspect the Cylinder 2 injector and harness for obvious damage, corrosion or disconnected connectors.
With ignition OFF, unplug the injector/heater connector and measure heater element resistance between pins. Compare to OEM spec. An open (OL) indicates a failed heater element or broken conductor.
With ignition ON and engine off, command the fuel heater ON using a scan tool (if available). Back-probe the connector and verify supply voltage to the heater and switching/ground signal from the ECM.
If no voltage is present at the connector when commanded, trace supply side: check fuses, relays, and power feed for continuity and voltage.
If voltage is present but no continuity through the heater, suspect open in harness or failed heater element. Perform wiggle test on harness while monitoring to find intermittent opens.
If heater element shows expected resistance but no current flows when commanded, check for a broken return/ground or an ECM driver fault. Measure for short to battery or short to ground as applicable.
To isolate ECM vs wiring/heater, swap the Cylinder 2 heater/injector connector with another cylinder's heater circuit (if harness/connector designs are identical) and see if the code follows the component or remains on Cylinder 2. Only swap if this is safe and recommended by OEM.
Repair or replace damaged wiring, connector or injector heater as indicated. Replace blown fuse/relay if failed.
Clear codes and perform test drive/cold-start cycles as needed to verify the repair and that the code does not return.

Likely causes

Broken or disconnected wire between ECM and Cylinder 2 heater
Corroded connector at the injector harness resulting in open/high resistance
Failed heater element inside the Cylinder 2 injector assembly

Fault status

⚠️ Status

Open or high resistance detected in Cylinder 2 fuel heater control circuit. ECM commanded heater ON but did not detect expected current/voltage response. Check wiring, connector, heater element and power/ground supply.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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