P0277 indicates the engine computer has detected abnormally high voltage on the control circuit for cylinder 6's fuel injector. In most cases this means the circuit is open — the computer is trying to energize the injector but cannot complete the electrical path. The vehicle may run rough or set additional misfire codes if cylinder 6 is not receiving fuel.
A broken wire, corroded terminal, or pushed-back pin in the injector connector is the most common cause of a high-voltage circuit code. The computer sees battery voltage because it cannot pull the circuit to ground.
An internally open injector coil will produce the same high-voltage reading as a wiring fault. Resistance testing or swapping injectors can isolate the failure.
Even if wiring is intact, corrosion, bent pins, or poor terminal tension at the injector connector can interrupt the circuit and trigger this code.
Physical damage to the engine harness from rubbing, heat, or animals can open the injector control wire. This is common on vehicles with aging or exposed harness routing.
The internal driver transistor in the engine computer can fail, but this is uncommon and should only be considered after all wiring and the injector itself are verified good.
Extended driving is not recommended. Cylinder 6 may not be receiving fuel, causing a misfire that can damage the catalytic converter over time and increase emissions.
Usually no. The vast majority of P0277 cases are caused by an open wire, corroded connector, or failed injector. The PCM should be the last component tested, not the first replaced.
Yes, with a digital multimeter. Measure the injector coil resistance and compare it to a known-good cylinder. If the reading is out of specification or infinite (open), the injector is likely faulty.
Yes. A corroded, loose, or partially disconnected connector can interrupt the circuit and produce the same high-voltage signal as a failed injector or broken wire.