P0271
Fix within a few daysCylinder 4 Fuel Injector Circuit High
Code P0271 means your Cylinder 4 fuel injector circuit has a high voltage or open fault. Common causes: Bad injector (60%), wiring issue (30%). Drivability: Limit driving, fix within days. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0271?
Limit driving, fix within a few days
Essential trips under 10 miles, avoid highways
Stop driving immediately if: Flashing Check Engine Light, loud engine noises, burning smell, significant power loss
Symptoms of P0271
- 1Engine misfire or rough idle
- 2Reduced engine power or poor acceleration
- 3Check Engine Light is on, possibly flashing
- 4Poor fuel economy
- 5Engine hesitation or stumbling
Common Causes of P0271
Parts most likely causing this code, ranked by probability
The fuel injector for cylinder 4 has an internal electrical open circuit or is mechanically stuck closed, preventing proper fuel delivery.
60% of P0271 cases are fixed by replacing this part
An open circuit, a short to voltage, or a poor connection in the wiring or connector leading to the cylinder 4 fuel injector prevents the correct electrical signal.
30% of P0271 cases are fixed by repairing this wiring
The engine computer's internal driver circuit for the cylinder 4 fuel injector is faulty, failing to send the correct signal.
10% of P0271 cases are fixed by replacing this part
Check These First (Before Buying Parts)
- Visually inspect the electrical connector and wiring for the cylinder 4 fuel injector for any obvious damage, corrosion, or loose connections.
- Listen for a distinct clicking sound from the cylinder 4 injector with the engine running (use a mechanic's stethoscope or long screwdriver to listen).
How to Diagnose P0271
- 1Visually inspect the wiring harness and electrical connector for the cylinder 4 fuel injector for any signs of damage, corrosion, or loose pins.
- 2With the engine off, disconnect the cylinder 4 fuel injector and measure its electrical resistance across the terminals using a multimeter. Compare the reading to factory specifications (typically 10-16 ohms). An 'OL' (open line) reading indicates a faulty injector.
- 3Use a noid light to check for an injector pulse at the cylinder 4 injector connector while cranking the engine. A flashing light indicates the PCM is sending a signal; no flash points to a wiring or PCM issue.
- 4If the noid light does not flash, check for proper power and ground signals at the injector connector using a multimeter.
- 5If the injector resistance is out of specification, replace the injector. If the resistance is good but the code persists, swap the cylinder 4 injector with an injector from another cylinder and see if the code moves to the new cylinder.
P0271 on Popular Vehicles
Ford F-150
2004-2010Ford F-150s, particularly with the 5.4L Triton engine, are known for fuel injector failures that can trigger P0271. These injectors can become clogged or fail electrically.
70% fixed by replacing the injector
Chevrolet Silverado
2007-2013On Chevrolet Silverado trucks, P0271 can sometimes be traced to wiring harness issues near the fuel injector connectors. Heat and vibration can cause insulation to wear or connections to loosen over time.
40% fixed by repairing wiring/connector
Honda Accord
2003-2012While less common, older Honda Accord models can experience P0271 due to aged or clogged fuel injectors. Fuel quality and maintenance history play a role in injector longevity.
60% fixed by replacing the injector
Frequently Asked Questions
What does P0271 mean?
P0271 indicates that the engine's computer has detected an electrical problem with the fuel injector circuit for cylinder 4. This means the circuit has a higher than expected voltage or an open circuit, preventing the injector from functioning correctly.
Can I drive with P0271?
Limit driving, fix within a few days. Driving with a P0271 code means your engine is misfiring on cylinder 4. This causes poor performance and can quickly lead to expensive damage to your catalytic converter if ignored.
Will P0271 clear itself?
No, P0271 will not clear itself. This code indicates a hard electrical fault or a component failure that requires diagnosis and repair. The Check Engine Light will remain on until the underlying issue is fixed and the code is cleared.
How do I fix P0271 myself?
Start by visually inspecting the injector wiring. If it looks good, test the resistance of the cylinder 4 fuel injector with a multimeter. If it's out of specification, replace the injector. If the injector tests good, use a noid light to check for a pulse at the injector connector to rule out wiring or PCM issues.
How much does it cost to fix P0271?
A DIY fix for P0271 typically costs $50-$200 for a new fuel injector and basic tools. If you take it to a professional shop, expect to pay $150-$500, which includes parts and 1-2 hours of labor for diagnosis and replacement.
P0271 keeps coming back - why?
If P0271 keeps returning, it means the initial repair did not address the root cause. This often happens if you only replaced the injector without properly checking the wiring harness for shorts or open circuits, or if the PCM itself has a rare internal fault.
Will P0271 fail emissions/smog test?
Yes, P0271 will cause your vehicle to fail an emissions or smog test. A misfiring cylinder significantly increases harmful emissions, and the active Check Engine Light is an automatic failure in most inspection programs.
What's the difference between P0271 and P0304?
P0271 specifically points to an electrical circuit issue with the cylinder 4 fuel injector (Circuit High). P0304 indicates a general misfire detected on cylinder 4, which can be caused by many things, including a P0271 fault, but also spark plugs, ignition coils, or compression issues.
P0271 on Ford F-150
On many Ford F-150 models, especially those with the 5.4L Triton engine, fuel injector failures are a common cause for P0271. Carbon buildup can also contribute to injector issues. Always check the injector's electrical resistance first.
Questions to Ask Your Mechanic
Did you test the resistance of the cylinder 4 fuel injector?
Good answer: Yes, I measured it at [X] ohms, which is within specification. Or, 'It was open circuit, so I replaced it.'
Did you check for injector pulse at the cylinder 4 connector with a noid light?
Good answer: Yes, I confirmed there is a pulse, so the PCM is sending the signal. Or, 'No pulse, so I'm tracing the wiring now.'
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - Requires electrical testing with a multimeter and potentially a noid light, along with basic mechanical skills to access and replace the injector.
Cost of Waiting
Continued misfires send unburned fuel to your catalytic converter, causing it to overheat and fail. A $50-$200 fuel injector job now prevents an $800-$2,500 catalytic converter replacement later.
While You're In There...
Always replace the O-rings when removing or installing a fuel injector to ensure a proper seal and prevent fuel leaks.
If the misfire has been ongoing, the spark plug in cylinder 4 may be fouled. Replacing all plugs ensures consistent ignition and prevents future misfires.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Noid light set
- Basic hand tools (sockets, wrenches)
- Fuel injector puller (if required for your vehicle)
P0271 is a common fuel system code. Most repairs involve replacing a single fuel injector, which is a straightforward job for an intermediate DIYer. Your engine will run smoothly again once fixed.
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Your Next Steps
Step 1: Visually inspect the wiring and connector for cylinder 4's fuel injector. Look for frayed wires, corrosion, or loose connections.
Step 2: If the wiring looks good, use a multimeter to test the resistance of the cylinder 4 fuel injector. If it's outside the specified range (usually 10-16 ohms), replace the injector.
Step 3: If the injector resistance is good, use a noid light to check for an injector pulse at the connector while cranking the engine. If there's no pulse, you'll need to diagnose the wiring back to the PCM or consider a PCM issue.