P01D4

What it means

P01D4 means the engine control unit has found that the injection timing on cylinder 5 is more advanced than commanded, so fuel is being delivered earlier than it should be. It is set when the measured or inferred injection timing for that cylinder strays beyond the allowed limit from the target. The code is mainly seen on diesel engines with electronically controlled injection, and the exact monitoring method depends on the engine.

Symptoms

• Engine management warning light on
• Diesel knock or rough running, often worse on cold start
• Uneven idle or misfire feel on one cylinder
• Loss of power or the engine running in limp mode
• Increased exhaust smoke or a stronger fuel smell
• Harder starting or erratic fuelling

Possible causes

• Faulty or sticking cylinder 5 injector (mechanical wear or internal leak)likely
• Wiring or connector fault in the cylinder 5 injector circuit (high resistance, chafing, corrosion)likely
• Incorrect fuel pressure or fuel rail pressure control problem affecting injection timingpossible
• Crankshaft or camshaft position sensor signal fault or timing correlation errorpossible
• Mechanical timing fault such as a jumped or stretched timing belt or chain, or a worn pump drive (engine dependent)possible
• Missing injector correction or coding data after injector replacement, or an outdated control unit calibrationrare
• Internal fault in the engine control unit injector driverrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine speed, load, temperature and fuel pressure when the fault set
2. Check for other related codes such as injector circuit, rail pressure, or crank and cam correlation faults, and deal with those first
3. Inspect the cylinder 5 injector wiring and connector for damage, corrosion, oil ingress and poor pin tension
4. Check live data for injector correction values or balance rates and compare cylinder 5 against the others
5. Compare actual and commanded fuel rail pressure at idle and under load, and check fuel supply, filters and fuel quality
6. Check crankshaft and camshaft sensor signals and their wiring, and verify the mechanical timing is correct using the manufacturer's procedure
7. Test the cylinder 5 injector electrically and for return flow or leakage using the procedure for that engine
8. Confirm that injector coding was done correctly if an injector has been replaced recently

How to fix

• Repair or replace damaged wiring, terminals or connectors in the cylinder 5 injector circuit
• Replace the faulty cylinder 5 injector and code or adapt it to the control unit as the manufacturer requires
• Correct fuel supply or rail pressure faults, including replacing blocked filters or faulty pressure components
• Replace faulty crankshaft or camshaft position sensors, or correct the mechanical timing fault
• Update or reflash the control unit calibration only where the manufacturer lists an outdated calibration as a known cause
• Repair or replace the control unit only after all other causes are ruled out

Can I keep driving?

Nearby codes

• P01D3GenericCylinder 5 Injection Timing Performance - Over Retarded
• P01D5GenericCylinder 6 Injection Timing Performance - Over Retarded