Code Definition

P1191 — Fuel Rail Pressure Build-up Too Slow

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

About P1191

P1191 is a manufacturer-specific powertrain diagnostic trouble code recorded for KGM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1191 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.

P1191 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

The high pressure common rail diesel fuel system uses an engine driven high pressure pump to charge the fuel rail, with a rail pressure sensor providing closed loop feedback to the Engine Control Module (ECM). DTC P1191 sets when, during cranking or acceleration, the ECM detects that actual rail pressure is building more slowly than the rate needed to start and run the engine. The ECM compares measured rail pressure against a target build rate over a set time window and flags this code when pressure fails to rise quickly enough, which points to a fuel supply or pressure control fault rather th...

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