P0279 code: Cylinder 7 Injector Circuit Low
P0279 means cylinder 7 Injector Circuit Low. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0279 means
This code appears on engines with at least seven cylinders — in practice mostly V8s and larger — and means the ECM measured lower-than-expected voltage on the cylinder 7 injector control circuit. Low-side faults typically come from a wire shorted to ground, an open in the circuit, or an injector coil that has shorted internally. It is an electrical diagnosis, not a fuel-delivery one: a clogged injector restricts flow without disturbing circuit voltage, so it sets misfire codes instead. With eight or more injectors to compare against, isolating cylinder 7's problem is straightforward — measure its injector resistance, inspect its harness leg, and swap-test against a neighbor if needed. Companion codes are P0207 (cylinder 7 injector circuit) and P0307 (cylinder 7 misfire). On V8s the two banks are numbered differently by different manufacturers, so confirm which physical cylinder is number 7 on your engine before testing.
P0279 symptoms
- Misfire attributed to cylinder 7
- Rough idle — often subtle on a V8, since seven cylinders still fire
- Reduced power and towing performance
- Check-engine light, flashing under sustained misfire
- Sometimes no drivability change if the fault is intermittent
What it costs to fix P0279
Typical range: $60–$450 · about ~0.5–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Fuel injector (single) | $50–$300 | ~0.5–2 hrs |
| Wiring/connector repair | $5–$50 | ~0.5–2 hrs |
Cylinder 7 sits toward the rear of a bank on most V8s, where access can be tight — engines needing intake manifold removal, and direct-injection engines with costlier injectors, run to the high end. Simple wiring repairs stay cheap.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0279 for my exact vehicle →
How to fix P0279
Moderate — doable at home with common tools and patience
- Locate cylinder 7 and note the freeze frame
V8 bank numbering differs between manufacturers, so check a cylinder-layout diagram for your engine before unplugging anything. Record the freeze-frame data and see whether P0207 or P0307 is stored too — a cylinder 7 misfire alongside it confirms the injector has actually dropped out rather than just flickering on the circuit monitor.
- Ohm injector 7 and two of its siblings
Unplug injector 7 and measure across its two terminals, then repeat on two other injectors with the same meter. High-impedance injectors are commonly cited around 11–18 ohms, but the side-by-side matters more than the figure: a reading on 7 noticeably lower than the rest means its winding is shorting internally and dragging the circuit down.
- Test the control wire for a path to ground
Disconnect the battery, unplug injector 7 and the ECM connector, and measure from the harness control pin to a clean engine ground; it should read open. Continuity means bare copper is touching metal somewhere. A grounded control wire can hold the injector open, so if you smell raw fuel or the engine floods on start-up, stop cranking to avoid hydrolock.
- Follow the harness behind the intake toward the firewall
Trace the cylinder 7 leg along the fuel rail to the back of the engine, where heat and engine rock wear insulation against brackets. If the intake has been off recently, look for a wire pinched under the manifold flange or a retaining clip that never went back on. Repair with soldered, heat-shrunk joints rather than tape.
- Replace a shorted injector, then recheck the driver
If 7's winding tested low, relieve fuel pressure, fit the new injector with fresh O-rings, clear codes, and drive. A shorted coil pulls extra current through the ECM's driver, so if P0279 returns with a good injector and a clean harness, that driver may have been damaged along the way — confirming it is shop work.
DIY or shop? Everything up to the injector swap is meter work a careful home mechanic can handle: finding cylinder 7, comparing injector resistances, and checking the control wire for a ground. Replacing a port injector on a V8 usually means lifting the fuel rail, which is manageable if you bleed off pressure properly and keep ignition sources away. It turns into shop work when the rail sits under the intake manifold, when the engine is direct-injected, or when the injector and wiring both test good and the ECM driver is the remaining suspect.
Tools for the DIY steps: Digital multimeter · Wiring diagram for your engine · Fuel pressure gauge with bleed valve · Injector O-ring kit · Solder and heat-shrink tubing
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0279.
Start a case with P0279 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0279?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0279: common questions
The engine barely feels rough — is P0279 still serious?
Somewhat, yes. Big engines hide a single misfiring cylinder well, but the catalytic converter still receives that cylinder's unburned fuel. Smoothness isn't a good gauge of catalyst risk, so treat the repair as prompt even if the engine feels smooth.
What does 'low' mean in this code?
The circuit voltage for cylinder 7's injector fell below the range the ECM expects — the typical signatures of a short to ground, a broken wire, or an injector coil that has shorted internally. It rules out fuel contamination and clogging as the cause.
How do I find cylinder 7 on my V8?
It depends on the manufacturer — some number one bank 1-2-3-4 and the other 5-6-7-8, while others alternate across banks. Look up the cylinder-numbering diagram for your specific engine, because testing or replacing the wrong bank's injector wastes time and money.
Injector or wiring — which is more likely?
Both are common enough that testing beats guessing. A quick resistance measurement at the injector answers most of it: a reading in line with the other seven means chase the harness and connector; a shorted or open reading means the injector itself failed.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0279 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0279 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.