The ISUZU P1093 code indicates an abnormally low fuel pressure in the common rail, detected by the engine control module (ECM). It is a critical code for Common Rail diesel engines, particularly for ISUZU models like the D-Max, where a loss of pressure can lead to engine stalling or a failure to start.
⚠️ Detailed Meaning of the ISUZU P1093 Code
This code is triggered when:
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➤ The differential pressure is –10 MPa for >15 s between 0 and 900 RPM, or
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➤ The pressure drops to –15 MPa for >15 s above 1200 RPM
This indicates that fuel is not reaching the injectors properly.
🧭 Probable Causes
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🔧 Clogged fuel filter — The most common Cause #1.
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🔧 Leak in the fuel circuit (porous hose, loose connection, faulty check valve, etc.)
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🔧 Faulty high-pressure fuel pump
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🔧 Faulty rail pressure sensor (FRP) or erroneous signal
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🔧 Stuck injector or internal leak
🛠️ Recommended Repair Procedure
1. Visual Inspection
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Check the entire low-pressure circuit (from the tank to the filter) up to the rail:
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Visible leaks,
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Cracked or damp hoses,
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Sensor electrical connectors.
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2. Replace the Fuel Filter
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If the filter has more than 20,000 to 30,000 km, replace it first.
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Ensure there is no air in the circuit (bleed it manually or with a diagnostic tool).
3. FRP Sensor Test
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Measure the voltage sent by the sensor during startup.
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Check with the diagnostic tool if the actual pressure matches the setpoint.
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If inconsistent → suspect the sensor or its wiring harness.
4. Pressure Test with OBD Scanner
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With the engine running or during startup, verify that the pressure rises above 250 bar (25 MPa).
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If the pressure remains low:
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Test the high-pressure pump (and the regulating valve).
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Test the injectors one by one for excessive return leakage.
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5. Injector Test (Return)
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Disconnect the return hoses and connect transparent tubes to check if an injector has abnormally high return flow (which would drop the rail pressure).
📌 Conclusion
The P1093 code on ISUZU is often due to a clogged fuel filter or an air or fuel leak, but it can also reveal a worn high-pressure pump or a faulty injector.