P029C
Cylinder 1 - Injector Restricted.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 9C
- FaultThe specific fault in that area
What it means
P029C is the generic code for a restricted fuel injector on cylinder 1. The engine control unit has judged that cylinder 1 is not receiving the fuel quantity it commands, usually from fuel trim, misfire or cylinder balance data, or from injector flow tests the ECU runs itself. The exact detection method differs between manufacturers and engines.
Symptoms
- Rough idle or a noticeable shake at idle
- Hesitation or flat spots under acceleration
- Misfire on cylinder 1, possibly with a flashing or steady engine warning light
- Poor fuel economy
- Hard starting or uneven running when cold
- Reduced power or the car going into limp mode
Possible causes
- Partially blocked or fouled cylinder 1 injector (deposits, varnish or debris)likely
- Poor fuel quality or contamination that has clogged the injector nozzle or filterpossible
- Low fuel pressure from a weak pump, clogged fuel filter or faulty pressure regulator affecting deliverypossible
- Wiring or connector fault on the cylinder 1 injector circuit giving weak or erratic injector operationpossible
- Carbon build-up on intake valves or in the combustion chamber on direct injection engines, upsetting the cylinder 1 fuel balancepossible
- Intake air leak or vacuum leak near cylinder 1 skewing the fuel correction for that cylinderrare
- Faulty or outdated ECU software or injector correction data (only where the manufacturer has a known issue)rare
How to diagnose
- Read all stored and pending codes and note the freeze frame data, including engine load, temperature and fuel trims
- Check for related misfire codes (P0301) or other injector codes, and look at live misfire counters and fuel trims
- Visually inspect the cylinder 1 injector connector and wiring for damage, corrosion, heat damage or poor pin tension
- Inspect for intake air leaks, split hoses and loose connections near cylinder 1
- Check fuel pressure against the manufacturer specification, both at idle and under load, and check the fuel filter if fitted as a serviceable item
- Measure injector resistance and check the injector drive signal and supply with a multimeter or scope, following the model-specific procedure
- Run an injector balance or cylinder contribution test and compare cylinder 1 with the others
- Inspect the injector spray pattern and flow on a test bench, or consider swapping with another cylinder to see if the fault follows the injector (procedure depends on the engine)
How to fix
- Professionally clean or replace the cylinder 1 injector if flow is restricted
- Replace the fuel filter and correct fuel pressure faults such as a failing pump or regulator
- Repair or replace damaged injector wiring or connectors
- Seal any intake leaks found near cylinder 1
- Clean carbon deposits from the intake tract on engines where this is a known problem, using the manufacturer's approved method
- Update the ECU software or apply injector correction values only if a known fault with the calibration has been identified for that model
Can I keep driving?
The car can usually be driven for a short time, but book it in soon because a restricted injector can cause misfires, a lean condition and possible catalytic converter or engine damage. If the engine light is flashing or the engine runs very roughly, stop driving and get it checked.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.