P0191 on GMC
Fuel Rail Pressure Sensor Circuit Range/Performance
P0191 on GMC vehicles indicates fuel rail pressure sensor circuit range/performance. Au7o has documented this code across 2 GMC models — most commonly on Sierra 2500HD, Sierra 3500HD. This code sets when the fuel rail pressure sensor's signal is out of its expected range or doesn't match what the computer expects for current conditions. On direct-injection and many modern engines, this sensor reports fuel pressure in the rail so the computer can precisely control fueling and the fuel pump. When the reading is implausible — too steady, erratic, or inconsistent with commanded pressure — this code is set, sometimes with hard starting, hesitation, or reduced power. It generally points to the sensor or its wiring, though an actual fuel-pressure problem can also trigger it. Typical repair costs on GMC range from $8,000 to $18,000, depending on the specific model and root cause.
Common Causes of P0191
- •Faulty fuel rail pressure sensor
- •Corroded, loose, or damaged sensor connector
- •Open, shorted, or high-resistance sensor wiring
- •Actual fuel pressure out of range (weak pump or regulator)
- •Restricted fuel filter or supply line
- •Loss of reference voltage or ground from the ECM/PCM
- •Faulty fuel pressure regulator or control valve
P0191 on GMC by Model
GMC Sierra 2500HD(1 issue)
- CP4.2 High-Pressure Fuel Pump Catastrophic Failure2011-2020
The Bosch CP4.2 high-pressure fuel injection pump used on the 2011-2016 LML and 2017-2020 L5P Duramax diesel engines is prone to catastrophic failure that destroys the entire fuel injection system. Unlike its predecessor the CP3, the CP4.2 lacks a roller element and relies solely on fuel for lubrication. When metal fatigue occurs, the pump shatters and sends metal debris throughout the entire high-pressure fuel system — contaminating all six injectors, the fuel rails, return lines, and feed lines. Total repair cost runs $8,000-18,000. A class action lawsuit was filed against GM. The same pump also fails in Ford 6.7 Power Stroke and Ram 6.7 Cummins of the same era.
GMC Sierra 3500HD(1 issue)
- CP4.2 High-Pressure Fuel Pump Catastrophic Failure2011-2020
The Sierra 3500HD Duramax diesel uses the same Bosch CP4.2 high-pressure fuel pump as the 2500HD. The pump is prone to catastrophic failure that destroys the entire fuel injection system (all 6 injectors, fuel rails, return lines). The 3500HD is often used for heavier towing and work applications, which places more sustained load on the high-pressure fuel system and may accelerate CP4.2 wear. Total system replacement costs $10,000-18,000. A CP3 conversion kit (Fleece FPE-CP3K-LML or FPE-CP3K-L5P) is strongly recommended as a preventive upgrade on any high-mileage Sierra 3500HD Duramax.
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View P0191 across all makes →Frequently Asked Questions
What does P0191 mean on GMC?▼
P0191 stands for "Fuel Rail Pressure Sensor Circuit Range/Performance." This code sets when the fuel rail pressure sensor's signal is out of its expected range or doesn't match what the computer expects for current conditions. On direct-injection and many modern engines, this sensor reports fuel pressure in the rail so the computer can precisely control fueling and the fuel pump. When the reading is implausible — too steady, erratic, or inconsistent with commanded pressure — this code is set, sometimes with hard starting, hesitation, or reduced power. It generally points to the sensor or its wiring, though an actual fuel-pressure problem can also trigger it. On GMC specifically, this code is documented across 2 models.
What causes P0191 on GMC vehicles?▼
Common causes on GMC: Faulty fuel rail pressure sensor, Corroded, loose, or damaged sensor connector, Open, shorted, or high-resistance sensor wiring, Actual fuel pressure out of range (weak pump or regulator), Restricted fuel filter or supply line. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0191 on a GMC?▼
Repair costs on GMC range from $8,000 to $18,000, depending on the specific model and root cause.
Which GMC models have P0191 documented?▼
Au7o has documented P0191 on 2 GMC models: Sierra 2500HD, Sierra 3500HD.