Code
P23D4
Generic
P — Powertrain
Cylinder 1 Fuel Heater Performance
AI status
Completed
Completed
100%
Causes
- Open or short in the fuel heater wiring or connector for cylinder 1
- Failed / burned-out fuel heater element
- Blown fuse or faulty relay supplying the heater circuit
- Poor ground or corroded connector pins
- PCM driver fault or internal control module failure
- Contaminated or clogged heater assembly preventing proper operation
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Cold-start difficulties or extended cranking time in low temperatures
- Rough idle or reduced driveability during warm-up
- Increased visible exhaust smoke during cold conditions (diesel)
- Diagnostic trouble codes stored for fuel-heater circuits or related systems
What to check
- Read and record freeze frame / freeze data and any additional related DTCs
- Visual inspection of heater, wiring harness, connector, and ground for damage/corrosion
- Confirm fuses and relays for fuel heater circuit are present and good
- Measure supply voltage at the heater power terminal with key ON and engine off
- Measure resistance of the heater element (unplugged) and compare to specification
- Back-probe control/ground side while commanding heater ON to confirm PCM output
Signal parameters
- Supply voltage to heater: should be near battery voltage when power is applied (~11–14.5 V) — verify in vehicle-specific spec
- Heater element resistance: typically low (ohm-range); compare to manufacturer spec
- Control signal: PCM may use switched ground or PWM; expect switching behavior when heater is commanded
- Current draw: measurable in amps when heater is energized — excessive or no current indicates fault
- No high-voltage signals expected; all measurements are low-voltage DC
Diagnostic algorithm
- Retrieve live data and stored freeze frame. Note whether code is continuous or intermittent and any related codes.
- Perform a visual inspection of the fuel heater, connector, wiring harness, and ground for damage, corrosion, or loose pins.
- Verify battery voltage and ground quality. Ensure battery is charged and vehicle grounds are clean and tight.
- Check fuses and relays for the fuel heater circuit; replace if blown and determine cause of blow if present.
- With ignition OFF, disconnect heater connector and measure resistance across the heater element. Compare to vehicle specification. Open or very high resistance indicates a failed heater; near-short indicates short.
- With key ON (engine OFF), measure voltage at the heater power terminal. If no battery voltage, trace fuse/relay/power circuit.
- Command the heater ON (if bi-directional control is available via scan tool) and back-probe the control terminal. Observe for switching/PWM from the PCM and confirm current flow to the heater. No PCM output suggests driver/PCM fault.
- Wiggle test wiring while monitoring voltage/current to find intermittent faults. Repair damaged wiring or connectors as needed.
- If heater element and wiring are good but PCM does not command correctly, consult manufacturer procedures and consider PCM tests or replacement only after confirming harness/ground/power.
- Clear codes and perform a road or cold-start test to verify repair. Re-scan for recurrence.
Likely causes
- Broken/disconnected wiring or corroded connector at the heater
- Heater element has lost continuity or excessive resistance
- Supply fuse or relay open (no power to heater)
- PCM output transistor or driver fault
- Low battery voltage or poor ground under load
Fault status
Status
Cylinder 1 fuel heater performance fault detected — check heater element, wiring, supply and PCM control.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Repair manuals
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