P026D
Fuel Injection Quantity A Higher Than Expected.
- 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)
- 6D
- FaultThe specific fault in that area
What it means
P026D means the engine control unit has calculated or measured that the fuel quantity being injected for fuel injection group 'A' is higher than the quantity it commanded or expected. It sets when the monitored fuel delivery, or the correction needed to hold the target air-fuel ratio, goes beyond its allowed limit. What 'A' refers to (a bank, injector group or injection stage) and how the quantity is judged depend on the manufacturer and engine.
Symptoms
- Engine warning light on
- Rich running or a smell of fuel from the exhaust
- Black smoke from the exhaust, especially on diesel engines
- Rough idle or uneven running
- Poor fuel economy
- Hesitation, reduced power or limp mode in some cases
Possible causes
- Leaking, sticking or over-delivering fuel injector(s)likely
- Fuel pressure too high, caused by a faulty pressure regulator, pressure control valve or pressure sensorlikely
- Faulty or contaminated air mass, manifold pressure or oxygen sensor causing the control unit to misjudge fuel demandpossible
- Wiring or connector fault on an injector or fuel pressure circuit, such as chafing, corrosion or high resistancepossible
- Restricted air intake or a boost or air leak that upsets the air-fuel calculationpossible
- Outdated or faulty control unit software or injector correction datarare
- Internal fault in the control unit or injector driverrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting load, rpm, temperature and fuel trim or injection quantity values when the fault set.
- Check for related codes covering fuel pressure, air flow, oxygen sensors, misfires or injector circuits, and diagnose those first.
- Inspect the injector and fuel pressure sensor wiring and connectors for damage, corrosion, oil or water ingress and poor pin tension.
- Inspect the air filter, intake pipework and sensor housings for blockages, leaks or contamination.
- With live data, compare actual and commanded fuel pressure and check fuel trims or injection quantity corrections, at idle and under load.
- Check the air flow and manifold pressure readings against expected values for the engine and conditions.
- Test the injectors for leakage, balance or correction values using the manufacturer's procedure, as the method depends on the engine type.
- Check for software updates or technical bulletins applicable to the vehicle and engine.
How to fix
- Replace any injector found to be leaking or over-delivering, and apply any injector coding the manufacturer requires.
- Repair or replace the faulty fuel pressure regulator, control valve or pressure sensor.
- Replace or clean faulty air flow, manifold pressure or oxygen sensors, and fix any intake leaks or restrictions.
- Repair damaged wiring or connectors in the injector or fuel pressure circuits.
- Update the control unit software only where an outdated or faulty calibration is a known cause for this vehicle.
Can I keep driving?
Short, gentle journeys are usually possible, but excess fuel can wash oil from the cylinder walls, damage the catalytic converter or cause engine damage over time. Get it diagnosed soon, and stop driving if the engine runs very roughly, smokes heavily or goes into limp mode.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.