P0279
Fix within a few daysThe engine computer detects a low voltage condition in the electrical circuit for the fuel injector on Cylinder 7.
Code P0279 means Cylinder 7's fuel injector circuit has a low voltage. Common causes: Faulty injector (50%), wiring issues (40%). Drivability: Limit driving, fix within a few days. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0279?
Limit driving, fix within a few days
Essential trips under 10 miles, avoid highways and heavy acceleration. Prolonged driving will cause damage.
Stop driving immediately if: Flashing Check Engine Light, significant power loss, loud knocking noises, burning smell, or rotten egg smell from the exhaust.
Symptoms of P0279
- 1Engine misfire or rough idle
- 2Reduced engine power
- 3Poor fuel economy
- 4Check Engine Light is on, possibly flashing
- 5Engine hesitation or stumbling
Common Causes of P0279
Parts most likely causing this code, ranked by probability
An internal electrical fault within the injector itself, such as a short or open circuit, causes the low voltage reading.
50% of P0279 cases are fixed by replacing this part
Damaged, corroded, or disconnected wiring or a faulty connector to the Cylinder 7 injector creates a low voltage condition.
40% of P0279 cases are fixed by repairing this wiring
A rare internal fault within the engine computer's driver circuit for Cylinder 7's injector causes the low voltage.
10% of P0279 cases are fixed by replacing this part
Check These First (Before Buying Parts)
- Visually inspect the wiring harness and connector for Cylinder 7's fuel injector for any obvious damage, fraying, or corrosion.
- Ensure the injector connector is fully seated and secure.
How to Diagnose P0279
- 1Visually inspect the wiring harness and connector for Cylinder 7's fuel injector for any damage, corrosion, or loose connections.
- 2Using a multimeter, check the resistance of the Cylinder 7 fuel injector. Compare it to specifications and other injectors.
- 3Using a noid light or multimeter, check for proper voltage and pulse signal at the Cylinder 7 injector connector while the engine is cranking.
- 4If the injector resistance is out of spec, replace the injector. If wiring is damaged, repair it.
- 5If the wiring and injector test good, swap the Cylinder 7 injector with an injector from another cylinder to see if the code moves.
P0279 on Popular Vehicles
Ford F-150
2004-2024On V8 F-150s, Cylinder 7 is typically on the passenger side, second from the rear. Wiring harness damage due to heat or rodent activity is a common cause, as is a failed injector.
85% fixed by replacing injector or repairing wiring
Chevrolet Silverado
2007-2024For Silverado V8 engines, Cylinder 7 is on the driver's side, second from the front. Injector failure is common, but also check for issues with the injector harness where it connects to the main engine harness.
80% fixed by replacing injector or repairing wiring
Dodge Ram
2003-2024On Ram trucks with Hemi V8 engines, Cylinder 7 is on the passenger side, second from the rear. These engines can experience injector failures, and the wiring can be susceptible to damage from heat or vibration.
85% fixed by replacing injector or repairing wiring
Frequently Asked Questions
What does P0279 mean?
P0279 indicates the engine's computer has detected a low voltage condition in the electrical circuit that controls the fuel injector for Cylinder 7.
Can I drive with P0279?
Limit driving, fix within a few days. Driving with a P0279 code means your engine is misfiring, which can cause significant damage to your catalytic converter and other engine components if ignored.
Will P0279 clear itself?
No, P0279 will not clear itself. The underlying electrical or mechanical fault causing the low circuit voltage must be diagnosed and repaired before the code will clear. Even if the light goes off temporarily, the problem is still present.
How do I fix P0279 myself?
Start by inspecting the wiring and connector for the Cylinder 7 fuel injector. If no damage is visible, test the injector's resistance with a multimeter. If the injector is faulty, replace it. If the wiring is damaged, repair it. If the injector tests good, check for proper voltage and pulse at the connector.
How much does it cost to fix P0279?
DIY repair costs for P0279 typically range from $50 to $200 for a new fuel injector. Professional repair at a shop usually costs between $150 and $500, which includes diagnosis and labor.
P0279 keeps coming back - why?
P0279 keeps coming back because the root cause was not fully addressed. This often happens if a wiring issue was overlooked, the replacement injector was faulty, or the problem is actually with the engine computer (PCM/ECM) which is less common.
Will P0279 fail emissions/smog test?
Yes, P0279 will cause your vehicle to fail an emissions or smog test. A misfiring cylinder increases harmful emissions, and the active Check Engine Light is an automatic failure in most testing programs.
What's the difference between P0279 and P0307?
P0279 specifically indicates an electrical issue with the Cylinder 7 fuel injector circuit (low voltage). P0307 indicates a general misfire detected on Cylinder 7, which can be caused by many things, including a faulty fuel injector, spark plug, or ignition coil.
P0279 on Ford F-150
On Ford F-150s, especially V8 models, P0279 is commonly caused by a faulty fuel injector or a damaged wiring harness to the injector. Cylinder 7 is often on the passenger side, towards the rear of the engine. Inspecting the connector for corrosion is a critical first step.
Questions to Ask Your Mechanic
Did you check the resistance of the Cylinder 7 fuel injector and compare it to specifications?
Good answer: Yes, I measured the resistance at X ohms, which is within the factory range of Y-Z ohms. The injector itself appears to be electrically sound.
What did you find when you tested the voltage and pulse signal at the injector connector?
Good answer: I confirmed there's proper battery voltage and a consistent pulse signal from the PCM. This tells me the wiring from the PCM to the injector is good.
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. This repair requires a multimeter for electrical testing and potentially a fuel injector removal tool, along with basic mechanical skills to access and replace the injector.
Cost of Waiting
Ignoring P0279 leads to a continuous misfire. This sends unburned fuel into your exhaust, which rapidly overheats and destroys your catalytic converter. A $50-$200 fuel injector repair now prevents a $1,200-$2,500 catalytic converter replacement later.
While You're In There...
A faulty injector can foul the spark plug. Replacing it ensures optimal combustion after the injector repair, and it's easily accessible once the injector is exposed.
While not a direct cause of P0279, a misfire from a bad injector can put stress on the ignition coil. It's often located right above the spark plug and easy to inspect/replace with the injector access.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Basic hand tools (sockets, wrenches)
- Noid light (optional, for injector pulse testing)
- Fuel injector removal tool (may be needed for some engines)
P0279 is a common fuel system code. Most repairs involve replacing a single fuel 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 and connector for the Cylinder 7 fuel injector. Look for any cuts, chafing, corrosion, or loose connections. Repair any damage found.
Step 2: If the wiring looks good, use a multimeter to test the resistance of the Cylinder 7 fuel injector. Compare the reading to factory specifications. If it's outside the range, replace the injector.
Step 3: If the injector resistance is good, use a noid light or multimeter to confirm the injector is receiving a proper pulse signal from the engine computer. If there's no pulse, the issue is likely wiring to the PCM or the PCM itself.