OBD codes / P0279
P0279
ModerateCylinder 7 Injector Circuit Low
A V8 masks a single dead cylinder well, which makes it tempting to ignore — but the unburned fuel from cylinder 7 still flows into that bank's catalytic converter and can overheat it. Fix it promptly even if the engine feels okay, and stop driving if the light flashes.
What this code 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.
Symptoms you might notice
- 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
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 →
Frequently asked
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 drivability seems fine.
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.
Seeing P0279 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0279 for my vehicleRelated trouble codes
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Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.