Faulty or sticking cylinder 4 fuel injector delivering outside its commanded timing; Wiring or connector fault in the cylinder 4 injector circuit (high resistance, chafing, corrosion); Crankshaft or camshaft position sensor signal error or poor correlation causing a timing offset; Fuel pressure problem such as a weak high-pressure pump, regulator fault or air or contamination in the fuel; Incorrect mechanical timing from a stretched or slipped timing belt or chain, or a worn drive; Missing injector correction or coding data after an injector or ECU replacement; Outdated or faulty ECU calibration, where a manufacturer update is known to address the fault.

P01D2

Cylinder 4 Injection Timing Performance - Over Advanced.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
D2: FaultThe specific fault in that area

What it means

P01D2 is a generic powertrain code meaning the engine control unit has detected that fuel injection timing on cylinder 4 is more advanced than commanded or expected. The ECU compares actual injection timing, usually derived from injector feedback, rail pressure behaviour or crank and cam position, against its target and sets the code when the difference exceeds a calibrated limit. It is most often seen on diesel engines, but exact monitoring methods vary by model and engine.

Symptoms

Engine management warning light on
Rough running or uneven idle
Diesel knock or harsh combustion noise, especially when cold
Hesitation or reduced power
Increased smoke or fuel smell from the exhaust
Hard starting or extended cranking

Possible causes

Faulty or sticking cylinder 4 fuel injector delivering outside its commanded timinglikely
Wiring or connector fault in the cylinder 4 injector circuit (high resistance, chafing, corrosion)likely
Crankshaft or camshaft position sensor signal error or poor correlation causing a timing offsetpossible
Fuel pressure problem such as a weak high-pressure pump, regulator fault or air or contamination in the fuelpossible
Incorrect mechanical timing from a stretched or slipped timing belt or chain, or a worn drivepossible
Missing injector correction or coding data after an injector or ECU replacementpossible
Outdated or faulty ECU calibration, where a manufacturer update is known to address the faultrare

How to diagnose

Read all stored and pending codes and freeze frame data, noting engine temperature, load, speed and rail pressure when the fault set
Check for related codes covering injectors, rail pressure, crank or cam sensors, or misfires, and diagnose those first
Visually inspect the cylinder 4 injector wiring, connector and earth points for damage, corrosion and poor pin tension
Inspect the fuel filter, fuel quality and low-pressure supply for air, water or contamination
Review live data for cylinder 4 injector correction values, balance rates and rail pressure compared with the other cylinders
Check crankshaft and camshaft sensor signals and correlation against the manufacturer's specification
Measure injector circuit resistance and carry out an injector leak-off or balance test as the engine's procedure allows
Verify mechanical timing and that injector coding matches the fitted injectors, following the model-specific procedure

How to fix

Repair or replace damaged wiring, connectors or terminals in the cylinder 4 injector circuit
Replace the faulty cylinder 4 injector and code or adapt it to the ECU as the manufacturer requires
Replace a faulty crankshaft or camshaft position sensor
Correct fuel supply faults by replacing the filter, draining contaminated fuel and repairing the pump or pressure control components
Correct the mechanical timing and replace worn timing drive components
Apply a manufacturer calibration update only if one is known to address this fault

Can I keep driving?

Medium severity

Short, gentle driving to a workshop is usually acceptable, but advanced injection timing can cause harsh combustion and engine damage over time. Avoid heavy loads and high revs, and stop if there is loud knocking, heavy smoke or the engine goes into limp mode.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.