P0191 on Cadillac: How to Diagnose & Fix
Fuel Rail Pressure Sensor Circuit Range/Performance
1 Cadillac model · 1 documented issue · 1 critical · $450-$950 repair
P0191 on Cadillac by model: symptoms, diagnosis and fix
The engine-mounted high-pressure fuel pump (HPFP) on the GM 3.6L direct-injection V6 is a known wear item that fails on the XTS, causing long crank/no-start (especially warm restart), rough idle, stalling and misfires. The most common codes are P0087 (fuel rail pressure too low), P0089 (fuel pressure regulator performance) and P0191 (rail pressure sensor), often with random misfire P0300. Because the high-pressure pump is cam-driven off the engine, a failing pump can drive adaptive fuel trims that mask early symptoms until it strands the car.
Common Symptoms
- Extended crank or no-start, worse when warm
- Rough idle / stalling
- Loss of power, sluggish throttle
- Check engine light with P0087/P0089
- Misfire / hesitation
- Decreased fuel economy
How to Fix
Perform a live high-side fuel-pressure test during acceleration and on a warm restart to confirm the HPFP versus injectors or the low-pressure (in-tank) pump. Replace the high-pressure fuel pump and its sealing/lifter components; many shops also replace the camshaft pump-drive lifter and inspect the lobe. Use fresh GM-spec fuel-system sealant and torque to spec to avoid leaks. OEM HPFP PN 12641740 (supersedes 12622475; aftermarket Delphi HM10007 / GDP106 cross-references). Reset fuel trims after the repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- High-pressure direct-injection fuel pump (engine-mounted HPFP) — naturally aspirated 3.6L V6OEM12691016Cross-refDelphi HM10007, API 119606-02729541, GM 12641740 (superseded)$75–$412
This is the pump for the standard naturally aspirated 3.6L V6 XTS (LFX/LGX), 2013-2019 — the large majority of XTS cars. GM has rolled the whole family of earlier numbers (including the 12641740 and 12622475 cited in the write-up) forwar…
- High-pressure direct-injection fuel pump — 3.6L twin-turbo LF3 (XTS V-Sport), 2014-2015OEM12658270Cross-refGM 19435427 (current supersession), cross-listed with 12642726 by aftermarket sellers$250–$820
It is NOT interchangeable with the naturally aspirated pump above — this is exactly the year/engine split that sends people home with a part that will not bolt on.
- High-pressure direct-injection fuel pump — 3.6L twin-turbo LF3 (XTS V-Sport), 2016-2019OEM12679089Cross-refGM 12672789 (superseded), GM 12652441 (superseded), GM 12666366 (superseded)$150–$435
Its application list also covers the ATS-V and CT4-V Blackwing, which are the LF4 twin-turbo cars — further confirmation this is the boosted-e
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Sources for this issue (1)
P0191 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0191 mean on a Cadillac?
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 Cadillac it is documented across 1 model: XTS.
What are the most common causes of P0191?
The most common causes of P0191 are: 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. The specific cause varies by vehicle.
How much does it cost to fix P0191 on a Cadillac?
Published repair estimates on Cadillac range from $450 to $950 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0191 on a different make?
View P0191 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.