P0191 on 2010 GMC Sierra 2500: Fuel Pressure Sensor Faults & Fixes (Gas & Diesel)

What's Unique About the 2010-2010 Gmc SIERRA 2500

For the 2010 Sierra 2500 with the 6.0L gas engine, the fuel system is controlled by a Fuel Pump Control Module (FPCM) that is notoriously prone to failure. It is mounted on the frame rail crossmember above the spare tire, where it is exposed to moisture and road salt, leading to severe corrosion on the module, its ground connection, and its wiring. For the 6.6L LMM Duramax diesel, the high-pressure common rail system operates at immense pressures (up to 26,000 PSI), making diagnosis sensitive to issues with the high-pressure pump, fuel pressure regulator (MPROP), or the rail sensor itself.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Hard starting, long crank times, or no-start condition.
• Engine stalls, especially under load or when coming to a stop.
• Rough running or idling.
• Reduced engine power, hesitation, or 'limp mode'.
• Engine feels gutless or falls on its face during acceleration.

Most Likely Causes

1. Failing Fuel Pump Control Module (FPCM) (6.0L Gas Engine) 🔴 High Probability The FPCM is mounted on the frame rail near the spare tire, where it is highly susceptible to water and salt intrusion, causing corrosion on the module, connector pins, and ground wire.
   How to confirm: Visually inspect the FPCM and its connector for green or white corrosion. Check for the related code P069E, which strongly points to a faulty FPCM. A common diagnostic trick is to bypass the module with jumper wires to see if the truck starts; if it does, the FPCM is bad. A scan tool can also be used to check for 12V power at the module.
   Typical fix: Replace the Fuel Pump Control Module. The new module may require programming, but some aftermarket options (like Dorman) come pre-programmed.
   Est. part cost: $70-$200
2. Faulty Fuel Rail Pressure Sensor (FRPS) 🔴 High Probability The sensor provides a critical signal that can become erratic with age and heat cycles. It's a common failure point on many modern vehicles and can fail electrically or get clogged with debris.
   How to confirm: With a scan tool, compare the 'desired' fuel rail pressure to the 'actual' pressure reading from the sensor. Then, connect a mechanical fuel pressure gauge to the rail. If the mechanical gauge shows correct pressure but the scan tool reading is incorrect or erratic, the sensor is bad. For the 6.0L gas engine, pressure should be 55-65 PSI with the key on, engine off. For the 6.6L diesel, idle pressure should be ~4,000-6,000 PSI and the sensor should read 0 PSI with the key on, engine off.
   Typical fix: Replace the Fuel Rail Pressure Sensor.
   Est. part cost: $40-$150
3. Damaged Wiring or Connector 🟡 Medium Probability Wiring to the FRPS (on top of the engine) or the FPCM (on the frame) can become brittle, chafed, or corroded over time. The FPCM ground wire on the frame is a particularly common failure point.
   How to confirm: Perform a visual inspection of the wiring harness and connectors for the FRPS and FPCM. Check for continuity and proper voltage at the sensor connector using a multimeter. Perform a voltage drop test on the FPCM power and ground wires.
   Typical fix: Repair or replace the damaged section of the wiring harness or the connector pigtail.
   Est. part cost: $15-$65
4. Weak In-Tank Fuel Pump / Lift Pump 🟡 Medium Probability
   How to confirm: If both the scan tool and a mechanical gauge show fuel pressure that is lower than specified (especially under load), the pump is likely weak. For the 6.0L gas engine, pressure should be 55-65 PSI with the key on, engine off. Listen for a hum from the tank when the key is turned on.
   Typical fix: Replace the in-tank fuel pump assembly.
   Est. part cost: $200-$500
5. Failing Fuel Pressure Regulator (6.6L Duramax) 🟡 Medium Probability The fuel pressure regulator (also called MPROP or FCA) on the high-pressure CP3 pump can wear out or get stuck due to fuel contamination, causing erratic rail pressure.
   How to confirm: Using a scan tool, monitor desired vs. actual rail pressure under load (e.g., wide-open throttle). If the actual pressure cannot keep up with desired pressure or is highly erratic, the regulator is a prime suspect. A 'bottle test' can also be performed on the fuel pressure relief valve to check for leakage.
   Typical fix: Replace the fuel pressure regulator on the high-pressure fuel pump. 🎬 Watch: Step-by-step guide to swapping the fuel pressure regulator.
   Est. part cost: $100-$250

Rare But Worth Checking

• Clogged Fuel Filter: This is a routine maintenance item that is often overlooked. It can restrict fuel flow and cause low pressure, triggering P0191, especially on Duramax engines under load.
• Failing High-Pressure Fuel Pump (6.6L Duramax): A weak high-pressure CP3 pump can fail to generate the commanded rail pressure under heavy load or when towing, triggering P0191 and P0087. This was the confirmed fix in a forum thread for a truck that only set the code when towing uphill.
• Fuel Contamination (Primarily 6.0L Gas Engine): As noted in GM TSB #PIP5151B, fuel system contamination (water, debris, excessive ethanol) can cause erratic fuel pressure readings and requires cleaning the entire fuel system.
• Faulty Powertrain Control Module (PCM): This is very rare. All other possibilities, especially sensor, wiring, and mechanical fuel system faults, should be exhausted before considering the PCM.

Diagnosis Steps

1. Scan for all stored DTCs. Note any other codes, especially P0087, P0088, or P069E, as they provide critical clues.
2. For 6.0L Gas engines, locate the Fuel Pump Control Module (FPCM) on the frame rail above the spare tire. Perform a thorough visual inspection of the module and its connector for any signs of corrosion or damage.
3. Visually inspect the wiring and connector for the Fuel Rail Pressure Sensor (FRPS) for any damage, corrosion, or loose connections.
4. Connect a scan tool and observe live data for 'Desired Fuel Rail Pressure' and 'Actual Fuel Rail Pressure'.
5. For 6.0L Gas: With the key on, engine off, pressure should be 55-65 PSI. Compare this to a mechanical gauge. If the mechanical gauge is correct but the scan tool is not, the sensor is bad.
6. For 6.6L Diesel: At idle, pressure should be around 4,000-6,000 PSI. At wide-open throttle, it should reach ~23,000-26,000 PSI. If actual pressure falls more than 2,000 PSI short of desired pressure under load, suspect a weak high-pressure pump or faulty regulator.
7. If the mechanical gauge shows correct pressure but the scan tool reading is incorrect, the Fuel Rail Pressure Sensor is faulty and should be replaced.
8. If no issues are found, perform a voltage and ground check on the FPCM and FRPS circuits with a multimeter to rule out an electrical fault.

Parts You'll Likely Need

• Fuel Pump Control Module (FPCM) (OEM #20759945) — Applies to the 6.0L Gas engine. Its location on the frame makes it extremely prone to corrosion and failure, causing erratic fuel pressure and triggering this code.
  Trusted brands: ACDelco, Dorman (OE Fix)
  OEM price range: $120-$200
  Aftermarket price range: $70-$195
• Fuel Rail Pressure Sensor (6.6L Duramax LMM) (OEM #98090186 (Bosch P/N: 0281002971)) — This sensor provides the direct signal for rail pressure on the high-pressure diesel system. It's a common failure point causing P0191. 🎬 See this video for diagnosing P0191 codes on Duramax engines.
  Trusted brands: Bosch (OEM), ACDelco
  OEM price range: $120-$275
  Aftermarket price range: $50-$150
• Fuel Rail Pressure Sensor (6.0L Gas) (OEM #12621292 (Supersedes 12589447, 12613350, 12614935)) — This sensor provides the signal that the ECM has deemed irrational. It is a common failure point on the gasoline engine's fuel rail.
  Trusted brands: ACDelco (GM OE), Delphi, Standard Motor Products
  OEM price range: $80-$150
  Aftermarket price range: $40-$90

Related Codes That Often Appear With This One

• P0087 — This code for 'Fuel Rail/System Pressure - Too Low' often appears with P0191 when there is a legitimate low-pressure condition from a weak pump, clogged filter, or failing high-pressure pump on a Duramax.
• P0088 — This code for 'Fuel Rail/System Pressure - Too High' can be set with P0191 if the sensor or fuel pressure regulator fails in a way that causes pressure to spike.
• P069E — This code indicates a fault in the Fuel Pump Control Module and is a strong indicator that the FPCM itself is the root cause of the P0191 on gasoline models.

Technical Service Bulletins (TSBs) & Recalls

• PIP4949E: Discusses hard start/no start conditions with DTCs P0087, P0088, P0191, or P128E.
• PIP5151B: Relates P0191 on gasoline engines to hard start, no start, or rough running, and highlights fuel contamination as a potential cause requiring a full system cleaning.

Platform-Specific Known Issues

• TSB #PIP5151B notes that on gasoline models, fuel contamination can be a cause for P0191 and other fuel pressure codes, requiring a full system cleaning if found.
• TSB #PIP4949E documents that P0191 can be associated with hard start or no-start conditions and may be present with codes P0087, P0088, or P128E.
• On 6.0L gas models, the ground wire for the FPCM is known to corrode at its attachment point on the frame, causing intermittent power loss to the module and erratic fuel pressure even if the module itself is okay.

Mechanic-Grade Diagnostic Values

• 6.0L Gas - Low-side fuel pressure (Key On, Engine Off) — expected: 55-65 PSI. Failure: Pressure below 55 PSI suggests a weak in-tank pump or FPCM issue.
• 6.6L Duramax - Fuel Rail Pressure Sensor (Key On, Engine Off) — expected: 0 PSI (0.5 Volts). Failure: A skewed reading (e.g., 145-261 PSI) indicates a faulty sensor, though it may not cause a no-start on its own.
• 6.6L Duramax - High-Pressure Fuel System Vacuum Test — expected: At least 12 inches of Hg. Failure: Less than 12 inches of Hg vacuum when cranking suggests a weak high-pressure pump or a leak in the system.
• 6.0L Gas - Fuel Rail Pressure Sensor Connector Voltage — expected: 5-volt reference on one pin, good ground on another.. Failure: Seeing ground on the 5V reference pin or voltage on the ground pin indicates a wiring issue, possibly swapped connectors further down the harness.
• 6.6L Duramax - Injector Return Flow Test — expected: Maximum 5 ml in 15 seconds for one injector.. Failure: Excessive return flow indicates leaking injectors, which prevents the system from building adequate rail pressure.

Hidden / Shadow Codes Worth Checking

• P128E: A GM-specific code related to fuel rail pressure sensor performance that is often cited in TSBs alongside P0191, P0087, and P0088. (see via Should be visible on most professional scan tools when present.)

Scan Tool Commands That Help

• Tech2 / GDS2: Command Rail Pressure — For the 6.6L Duramax, a technician can command rail pressure to a high value (e.g., 17,400 PSI) at idle to perform an enhanced injector return flow test, helping to isolate leaking injectors without a test drive.
• Tech2 / GDS2: Fuel Pump On/Off — For the 6.0L gas engine, this command verifies if the Fuel Pump Control Module (FPCM) is receiving the command from the ECM and is capable of activating the fuel pump.

Wiring & Ground Locations

• Fuel Pump Control Module (FPCM) — On the frame rail crossmember, located above the spare tire.. This location makes the module, its connector, and its ground wire extremely vulnerable to corrosion from road salt and moisture, which is a primary cause of P0191 on the 6.0L gas engine.
• FPCM Fuses (Underhood Fuse Block) — In the main engine fuse box on the driver's side. Specifically, fuses #20 (F/PMP), #21 (FPCM), and #56 (FPCM-IGN) are related to the module.. Before replacing the FPCM, these three fuses should be tested to rule out a simple electrical supply issue to the module.
• 6.0L Gas Fuel Rail Pressure Sensor — Under the vehicle, mounted directly on the main fuel supply line between the tank and the engine.. Unlike many vehicles where the sensor is on the engine's fuel rail, on this specific gas model it is on the low-pressure supply line. Its under-vehicle location exposes its connector to potential corrosion.

Real Owner Repair Stories

• Reddit user in r/Duramax (2008 LMM Duramax (same engine/fuel system as 2010) with 177k miles) — P0087 code (low rail pressure), frequent 'change fuel filter' messages, and going into limp mode.
  ❌ Tried (didn't work) Changing the fuel filter multiple times.
  ✅ What actually fixed it Installing a fuel pressure relief valve 'race plug'. The original valve was likely wearing out and bleeding off pressure under load, a common issue. Another user with similar symptoms and 305k miles also found the race plug worked for a time, indicating the relief valve is a common wear item.

OEM Part Supersession History

• 13501024, 15213110, 20850907, 25785013, 25854536, 25967325 → 20759945 — GM regularly updates service parts to integrate new materials and technologies for improved reliability.
  Heads up: The replacement FPCM (20759945) requires programming to the vehicle's VIN to function correctly. Some aftermarket suppliers offer pre-programmed modules.
• 12589447, 12613350, 12614935 → 12621292 — Standard part evolution and consolidation for the 6.0L gas engine's fuel pressure sensor.