Code P0273 indicates that the engine control module has detected abnormally low voltage in the fuel injector circuit for cylinder 5. This typically points to a short to ground, excessive resistance, or an internal failure within the injector that is pulling the circuit voltage down below the expected threshold.
The cylinder 5 injector may have an internal short to ground or coil failure, causing it to draw too much current and drop the circuit voltage.
The signal wire in the injector harness may be chafed or damaged, allowing it to contact the engine block or chassis ground before reaching the injector.
Corrosion, spread pins, or a loose connection at the cylinder 5 injector plug can introduce high resistance into the circuit, triggering a low voltage code.
In rare cases, the internal driver transistor for cylinder 5 inside the engine computer may have failed, though this is far less common than wiring or injector failures.
It is not recommended. A malfunctioning injector can cause a severe misfire, which may lead to unburned fuel entering the exhaust and causing expensive catalytic converter damage.
Not necessarily. While a failed injector is the most common cause, the code refers to the entire electrical circuit. A shorted wire or poor connection will trigger the same code.
Rarely. Mechanics and DIYers often misdiagnose a low circuit code as a failed PCM. The engine computer is almost never the root cause; the issue is typically a failed injector or a wiring short.
Unplug the injector and test the circuit. If the circuit voltage returns to normal with the injector unplugged, the injector is likely shorted internally. If the circuit remains low with the injector unplugged, the wiring harness is likely shorted to ground.