P2056 indicates that the powertrain control module (PCM) has detected an open circuit for the reductant injection valve on bank 2, unit 2. This valve meters diesel exhaust fluid (DEF) into the exhaust stream for NOx reduction; when its control circuit is interrupted, the system cannot operate properly and the engine may run in a reduced‑power mode to meet emissions limits.
The internal windings of the DEF injector can break, creating an open circuit that the PCM detects. This is the most common source of the fault.
Chafed wires, broken pins, corrosion, or poor connections in the harness leading to the valve can interrupt the control signal and cause an open circuit.
A dedicated fuse or relay that supplies power to the reductant injector may have failed, cutting off the circuit and triggering the code.
Some systems monitor downstream conditions before activating the injector; if those sensors send invalid data, the PCM may not energize the valve, mimicking an open circuit.
Rarely, the engine computer itself can fail to provide the correct output to the valve, but this is far less common than the other causes and should be investigated only after ruling out external faults.
No. In the vast majority of cases the fault lies with the valve, wiring, or a blown fuse. PCM replacement is rarely needed and should only be considered after all other components have been verified as good.
You can usually drive in a limited‑power mode, but the SCR system will be disabled, leading to higher emissions and possible regulatory non‑compliance. It is advisable to repair the issue promptly.
It means there is no complete electrical path for the valve’s control circuit; the PCM cannot send current to operate the injector, so it records an open‑circuit fault.
Clearing the code will turn off the warning light temporarily, but if the underlying fault (e.g., a failed valve or broken wire) is not repaired, the code will return as soon as the system runs its self‑test.