Code Definition

P1094 — Fuel Rail Pressure Too Low at Idle or During Fuel Cut

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Isuzu

About P1094

P1094 is a manufacturer-specific powertrain diagnostic trouble code recorded for Isuzu vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1094 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1094 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

On these Isuzu common rail diesel engines the Engine Control Module (ECM) commands the high pressure pump and the regulator to hold a minimum rail pressure at idle and during fuel cut, such as on deceleration when injection stops. DTC P1094 sets when the ECM detects rail pressure below the defined lower limit despite a valid pump or regulator command, persisting through the timeout at idle or during a fuel cut event. Because demand is low in these conditions, the fault usually means pressure is leaking away faster than it can be held, through a regulator or relief valve, injector back leakage,...

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