P0278
Fix within a few daysThe engine computer detects an electrical problem with the fuel injector for cylinder 6, specifically a high voltage or open circuit.
Code P0278 means Cylinder 6 Fuel Injector Circuit High. Common causes: Faulty injector (60%), wiring issue (30%), PCM fault (10%). Drivability: Limit driving, fix within a few days. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0278?
Limit driving, fix within a few days
Essential trips under 10 miles, avoid highways and heavy acceleration. Immediate repair needed to prevent further damage.
Stop driving immediately if: Flashing Check Engine Light, loud banging noises from the engine, strong rotten egg smell from the exhaust, significant power loss, or engine stalling.
Symptoms of P0278
- 1Check Engine Light is on
- 2Engine misfire or rough idle
- 3Reduced engine power
- 4Engine hesitation during acceleration
- 5Poor fuel economy
- 6Strong fuel smell from the exhaust
Common Causes of P0278
Parts most likely causing this code, ranked by probability
An internal electrical fault within the injector itself, such as an open circuit or high resistance, causes the PCM to detect a 'high' circuit condition.
60% of P0278 cases are fixed by replacing this part
Damaged, corroded, or loose wiring or a faulty connector to the cylinder 6 fuel injector can create an open circuit or high resistance, triggering the code.
30% of P0278 cases are fixed by repairing or replacing wiring
A rare internal fault within the PCM's driver circuit for the cylinder 6 injector can cause it to incorrectly report a high circuit condition.
10% of P0278 cases are fixed by replacing the PCM
Check These First (Before Buying Parts)
- Visually inspect the wiring and connector for the cylinder 6 fuel injector for any signs of damage, fraying, corrosion, or loose connections.
- Ensure the fuel injector connector is fully seated and secure.
How to Diagnose P0278
- 1Visually inspect the wiring harness and connector for cylinder 6 fuel injector for any damage, corrosion, or loose connections.
- 2Using a multimeter, check the resistance of the cylinder 6 fuel injector. Compare it to specifications and other injectors.
- 3With the engine running, use a noid light or oscilloscope to check for proper pulse signal at the cylinder 6 injector connector.
- 4If possible, swap the cylinder 6 fuel injector with an injector from another cylinder and see if the code moves to the new cylinder.
- 5If all other checks pass, test the PCM's driver circuit for the cylinder 6 injector (requires advanced diagnostic tools).
P0278 on Popular Vehicles
Ford F-150
2011-2024Ford F-150s, particularly EcoBoost models, are known to experience fuel injector failures that can trigger P0278. The injector's internal coil can fail, leading to an open circuit.
70% fixed by replacing the injector
Chevrolet Silverado
2007-2024On Chevrolet Silverado trucks, P0278 can be caused by a failing fuel injector or, less commonly, a corroded connector at the injector. Inspect the connector carefully for green corrosion.
65% fixed by replacing the injector, 25% by wiring repair
Ram 1500
2009-2024Ram 1500s with the Hemi engine can sometimes develop P0278 due to injector failure or issues with the wiring harness where it passes near hot engine components, leading to insulation damage.
60% fixed by replacing the injector, 30% by wiring repair
Frequently Asked Questions
What does P0278 mean?
P0278 indicates that your vehicle's Powertrain Control Module (PCM) has detected an electrical problem with the fuel injector for cylinder 6, specifically a high voltage or an open circuit in its electrical path.
Can I drive with P0278?
Limit driving, fix within a few days. Driving with a P0278 code means cylinder 6 is likely misfiring. This sends unburned fuel into your exhaust, which can quickly damage your catalytic converter. Drive only for essential, short trips until repaired.
Will P0278 clear itself?
No, P0278 will not clear itself. This code indicates a hard electrical fault that requires diagnosis and repair. The Check Engine Light will remain on until the underlying issue is fixed and the code is cleared, either by the vehicle's self-diagnostic system after multiple good drive cycles or with a scan tool.
How do I fix P0278 myself?
Start by visually inspecting the wiring and connector for the cylinder 6 fuel injector. If no damage is found, test the injector's resistance with a multimeter. If the resistance is out of specification, replace the cylinder 6 fuel injector. If resistance is good, check the injector pulse with a noid light.
How much does it cost to fix P0278?
DIY repair costs for P0278 typically range from $50-$200, primarily for a new fuel injector. Professional repair at a shop will cost $150-$500, which includes parts, labor, and diagnostic fees.
P0278 keeps coming back - why?
If P0278 keeps returning, it means the root cause was not fully addressed. This often happens if you replaced the injector but the wiring harness still has an intermittent fault, or if the PCM itself has a rare internal issue. Thoroughly re-inspect wiring and test the circuit.
Will P0278 fail emissions/smog test?
Yes, P0278 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on is an automatic failure in most jurisdictions, and a misfiring cylinder will also lead to high emissions readings.
What's the difference between P0278 and P0306?
P0278 specifically indicates an electrical circuit problem with the cylinder 6 fuel injector (Circuit High). P0306 indicates a general misfire detected in cylinder 6, which could be caused by the injector, spark plug, ignition coil, or engine mechanical issues. P0278 is a more specific diagnosis of the injector's electrical health.
P0278 on Ford F-150?
On Ford F-150s, especially those with EcoBoost engines, P0278 is often caused by a faulty fuel injector. These injectors can experience internal electrical failures or become clogged, leading to circuit issues. Always check the wiring first, but be prepared to replace the injector.
Questions to Ask Your Mechanic
Did you test the resistance of the cylinder 6 fuel injector and compare it to specifications?
Good answer: Yes, the injector resistance was X ohms, which is outside the specified range of Y-Z ohms. We confirmed it's an internal injector fault.
What did you find when inspecting the wiring harness and connector for the cylinder 6 injector?
Good answer: We found some corrosion in the connector pins, which was causing high resistance. After cleaning and applying dielectric grease, the circuit tested good. Or, 'The wiring insulation was chafed, causing an intermittent open circuit.'
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 a multimeter and basic electrical diagnostic skills, along with the ability to safely remove and replace a fuel injector.
Cost of Waiting
Ignoring P0278 means cylinder 6 is misfiring. This sends raw, unburned fuel into your exhaust system, which rapidly overheats and destroys your catalytic converter. A $50-$200 fuel injector replacement now prevents a $800-$2,500 catalytic converter replacement later.
While You're In There...
These seals are removed and often damaged during injector replacement. Replacing them prevents fuel leaks and ensures a proper seal.
Depending on the engine design, the fuel rail may need to be removed, and its seals should be replaced to prevent vacuum or fuel leaks.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Basic hand tools (sockets, wrenches, screwdrivers)
- Noid light (optional, but helpful for injector pulse check)
- Fuel injector O-ring kit
P0278 is a common electrical fault for a fuel injector. Most repairs are straightforward, involving replacing the injector or repairing a wire, and your engine will run smoothly again afterward.
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Your Next Steps
Step 1: Visually inspect the wiring harness and connector for cylinder 6. Look for any cuts, chafing, corrosion, or loose pins. Repair any damage found.
Step 2: If wiring looks good, use a multimeter to test the resistance of the cylinder 6 fuel injector. If it's outside the manufacturer's specification (usually 10-16 ohms), replace the injector.
Step 3: If resistance is good, use a noid light to confirm the PCM is sending a pulse to the injector. If there's no pulse, the issue could be wiring back to the PCM or the PCM itself. If there is a pulse, but the injector resistance is good, the injector may still be faulty mechanically, or the PCM is misinterpreting the circuit.