Cylinder 1 injector sticking open or with a worn or damaged seat or needle; Carbon or debris holding the injector nozzle partly open; Damaged or hardened injector seals or O-rings allowing fuel to seep past; Fuel pressure regulator fault or excessive fuel pressure (where fitted); Wiring or connector fault causing incorrect injector operation on cylinder 1; Engine control unit fault or outdated calibration affecting leak detection.

P029D

Cylinder 1 - Injector Leaking.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
9D: FaultThe specific fault in that area

What it means

P029D is a generic code meaning the engine control unit has detected that the fuel injector on cylinder 1 is leaking, so fuel is likely entering the cylinder when it should not. It is usually set from fuel rail pressure behaviour after shut-down or during overrun, or from fuel trim and combustion data that point to excess fuel on that cylinder. Exact detection methods vary by engine and fuel system.

Symptoms

Hard starting or long cranking, especially when hot
Rough idle or misfire on cylinder 1
Smell of fuel from the exhaust or engine bay
Fuel rail pressure dropping quickly after switching off
Poor fuel economy or black smoke
Engine warning light on, possibly with misfire or fuel trim codes

Possible causes

Cylinder 1 injector sticking open or with a worn or damaged seat or needlelikely
Carbon or debris holding the injector nozzle partly openlikely
Damaged or hardened injector seals or O-rings allowing fuel to seep pastpossible
Fuel pressure regulator fault or excessive fuel pressure (where fitted)possible
Wiring or connector fault causing incorrect injector operation on cylinder 1possible
Engine control unit fault or outdated calibration affecting leak detectionrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including fuel trims, rail pressure and engine temperature
Check for related codes such as misfires, fuel trim or fuel pressure faults and deal with those causes first if present
Inspect the cylinder 1 injector connector, wiring and seals for damage, corrosion, fuel staining or looseness
Check for fuel smell, wet injector area or fuel in the engine oil (a rising oil level or fuel-smelling oil is a warning sign)
Monitor fuel rail pressure with a scan tool at idle and after switch-off to see if it falls faster than the manufacturer specifies
Compare cylinder 1 misfire counts and short-term fuel trim against the other cylinders
Test injector electrical resistance and operation against the manufacturer's specification
Carry out an injector leak-down or flow test, following the procedure for that specific engine and fuel system

How to fix

Replace the cylinder 1 injector if it is leaking or fails the flow and leak tests
Renew injector seals, O-rings and washers if the leak is external or at the seat
Repair or replace damaged wiring or connectors to the cylinder 1 injector
Replace a faulty fuel pressure regulator or correct a fuel pressure fault where the system has one
Change the engine oil and filter if fuel dilution is confirmed
Update the engine control unit software only if the manufacturer lists an outdated calibration as a known cause

Can I keep driving?

High severity

Limit driving and have it checked promptly, because leaking fuel can wash the cylinder walls, dilute the engine oil and damage the engine or catalytic converter. If you smell fuel or the engine runs very roughly, stop driving and arrange recovery.

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