P0271: Cylinder 4 fuel injector circuit reads high voltage
Injector 4 circuit high / cylinder 4 injector circuit high
Severity: Severity not verified — if the car runs badly, have it inspected
No source here rates the urgency of an injector circuit fault, so the class is not verified. One cylinder may get too little or too much fuel, so the engine can run rough.
P0271 in short
P0271 means the engine computer found the cylinder 4 fuel injector circuit reading high voltage. TroubleCodes.net lists a short to a positive voltage in the wiring, a faulty injector or the engine computer as the likely causes. Have it checked if the engine runs rough or loses power.
The computer drives each fuel injector through its own circuit and watches the voltage on it. P0271 is the code for cylinder 4: the voltage stayed high compared with what the computer expects.
TroubleCodes.net gives the likely causes as a short to a positive voltage in the wiring, the injector itself, or the engine computer. The code names one cylinder, so the check starts at that injector and its harness.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Wire shorted to positive voltage in the cylinder 4 injector circuit
Common general cause- Why it ranks here
- TroubleCodes.net lists the wiring fault first, and the Delaware list defines the code as a circuit fault, not a part fault.
- What would change this
- Rises if the harness is chafed, pinched or the connector is damaged. Falls if the wiring tests good.
Cause 2: Faulty injector on cylinder 4
Common general cause- Why it ranks here
- The injector is listed by TroubleCodes.net next to the wiring as a likely cause.
- What would change this
- Rises if the injector coil reading is out of range or it does not click. Falls if it tests like the other injectors.
Cause 3: Engine computer driver
Possible — needs testing- Why it ranks here
- The engine computer is listed last by TroubleCodes.net; check it only after the wiring and injector pass.
- What would change this
- Rises if the circuit and injector are good but the fault stays. Falls if a wiring or injector fault is found.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: With the engine off, look at the cylinder 4 injector connector and harness for chafing, corrosion or damage.
IfDamage, chafing or corrosion is found
It meansRepair the wiring or connector first.
Points to: Wire shorted to positive voltage in the cylinder 4 injector circuit
IfThe wiring looks sound
It meansTest the injector.
Step 2: Have the injector coil resistance measured and compared with specification and with the other injectors.
Warning:Injectors sit on a fuel rail that can hold pressure and fuel is flammable; a shop should relieve pressure and handle it. Some diesel injector circuits carry high voltage.
IfResistance is out of range
It meansThe injector is faulty.
IfResistance is normal
It meansLook for a wiring fault that comes and goes, or an engine computer driver fault.
Symptoms
- Check engine light
- Rough running or misfire on one cylinder
Compare with: Car shaking with the check engine light on
How to fix
Step 1: With the engine off and cool, check that the injector connector for that cylinder is fully seated and free of corrosion.
Parts and cost context
- Fuel injector:Test the injector and wiring before replacing; labor varies, get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P0271 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0271 yet.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error