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DTC codes / P2Axx · Hybrid propulsion / P2A78
P2A78 indicates that the powertrain control module (PCM) has detected a voltage signal from the alternative fuel hydraulic pump pressure sensor that is higher than the expected range for the current operating conditions. This sensor monitors hydraulic pressure in an alternative fuel system, such as a compressed natural gas (CNG) or propane injection setup, and the high signal typically points to an open circuit, a short to voltage, or a faulty sensor.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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