What P0279 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.
Each fuel injector is a solenoid switched by a driver in the engine computer. The module watches the electrical behaviour of every injector circuit and, on many engines, how much each cylinder contributes to engine speed. A cylinder-specific code narrows the fault to one injector, its wiring or its driver.
Cylinder numbering is set by the manufacturer, so check the cylinder layout for your engine to find cylinder 7; it is not always the one nearest the timing belt or chain.
What “Circuit Low” means here
"Low" means the signal or control voltage fell below the minimum the module expects. For a controlled component such as a solenoid, relay or motor, "low" means the voltage the module sees on the control circuit is lower than it should be for the commanded state — commonly a short to ground or a missing supply, depending on how the circuit is switched.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0279:
- Misfire on the affected cylinder
- Rough idle and loss of power
- Fuel smell or smoke if an injector sticks open
- Higher fuel use
Where to start diagnosing P0279
- Inspect the injector connector and harness for the affected cylinder; fuel-soaked or heat-damaged connectors are common.
- Measure injector coil resistance and compare with specification and with the other injectors.
- Use a noid light or scope to confirm the injector is being pulsed.
- Swap the injector to another cylinder where practical and see if the fault follows it.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0279. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Engine RPM (PID 0x0C) | Unstable idle speed is a sign of an inactive cylinder. |
| Short and long term fuel trim (PIDs 0x06–0x09) | A dead injector usually drives trims lean. |
| Misfire counts | Available through Mode 06 on many vehicles; shows which cylinder is misfiring. |
Related codes
Codes from the same fuel injector circuit family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0207 | Injector Circuit/Open - Cylinder 7 |
| P0275 | Cylinder 5 Contribution/Balance |
| P0276 | Cylinder 6 Injector Circuit Low |
| P0277 | Cylinder 6 Injector Circuit High |
| P0278 | Cylinder 6 Contribution/Balance |
| P0280 | Cylinder 7 Injector Circuit High |
| P0281 | Cylinder 7 Contribution/Balance |
| P0282 | Cylinder 8 Injector Circuit Low |
Further reading
Frequently Asked Questions
What does P0279 mean?
P0279 is the generic SAE J2012 code for "Cylinder 7 Injector Circuit Low". In plain terms, it means the engine computer has detected a "circuit low" fault on the fuel injector circuit for cylinder 7.
Can I keep driving with P0279?
A cylinder that is not firing can overheat the catalytic converter. Limit driving and avoid high loads until it is fixed.
What should I check first for P0279?
Inspect the injector connector and harness for the affected cylinder; fuel-soaked or heat-damaged connectors are common.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.