Aston Martin diagnostic trouble code
P0191: Fuel Rail Pressure Sensor Range/Performance
Use this reference to understand the recorded condition, confirm the available V8 Vantage or DB9 manual coverage, and follow the documented diagnostic checks before replacing parts.
- Code family
- Powertrain
- Vehicle system
- Fuel and air
- Manual coverage
- V8 Vantage, DB9
- Warning-lamp status
- V8 Vantage: MIL; DB9: MIL
What Aston Martin code P0191 means
Fuel Rail Pressure Sensor Range/Performance
DB9 preliminary diagnostic manual · section 2-56
Manufacturer fault-analysis procedure
Manual fault definition
P0191 - Fuel rail pressure sensor range or performance
Cautions and notes
CAUTION: This code may be generated in the
Primary or Secondary Powertrain Control Module
(PCM) Check that you are working on the correct
half of the engine.
NOTE: Fuel rail pressure is normally about 40 psi above
manifold pressure.
If both fuel rail pressures are approximately 40
psi above manifold pressure, go to step 4.
If either sensor is indicating other than approximately 40 psi, switch off the engine. Allow the
residual fuel pressure to dissipate. Disconnect
both sensors. Remove the sensors and swap them
to the opposite fuel rail. Reconnect the sensors.
Primary or Secondary Powertrain Control Module
(PCM) Check that you are working on the correct
half of the engine.
NOTE: Fuel rail pressure is normally about 40 psi above
manifold pressure.
If both fuel rail pressures are approximately 40
psi above manifold pressure, go to step 4.
If either sensor is indicating other than approximately 40 psi, switch off the engine. Allow the
residual fuel pressure to dissipate. Disconnect
both sensors. Remove the sensors and swap them
to the opposite fuel rail. Reconnect the sensors.
Test sequence and decision path
1. Connect the WDS or scan tool. Confirm that a
code P0191 is logged.
2. Using the datalogger, monitor both fuel rail pressure signals during a KOER test.
3. Rerun the KOER test and fuel rail pressure comparison.
If the erroneous pressure reading has swapped to
the other fuel rail, replace the faulty pressure sensor. Clear the P0191 code and rerun the KOER
test to ensure that the problem is resolved.
If the erroneous reading remains on the original
fuel rail, the fault is not caused by the pressure
sensor, check for fuel pump DTCs and analyse
the fault for a fuel pump problem.
4. Check the fuel rail pressure sensor connections
and harness.
If no electrical fault is detected, the problem is
not present at this time. Treat this as an intermittent problem.
If any electrical fault is detected, service the wiring as necessary. Clear the P0191 code and run a
KOER test to ensure that the problem is resolved.
Open the corresponding manual page for wiring diagrams and figures
code P0191 is logged.
2. Using the datalogger, monitor both fuel rail pressure signals during a KOER test.
3. Rerun the KOER test and fuel rail pressure comparison.
If the erroneous pressure reading has swapped to
the other fuel rail, replace the faulty pressure sensor. Clear the P0191 code and rerun the KOER
test to ensure that the problem is resolved.
If the erroneous reading remains on the original
fuel rail, the fault is not caused by the pressure
sensor, check for fuel pump DTCs and analyse
the fault for a fuel pump problem.
4. Check the fuel rail pressure sensor connections
and harness.
If no electrical fault is detected, the problem is
not present at this time. Treat this as an intermittent problem.
If any electrical fault is detected, service the wiring as necessary. Clear the P0191 code and run a
KOER test to ensure that the problem is resolved.
Supporting owner context
What owners have reported
One owner case reported P0191 alongside rough running and improvement after throttle-body cleaning. That outcome is anecdotal and does not establish the cause, so use the manufacturer checks for the stored code.
This is supporting owner-reported context, not a replacement for the manufacturer procedure or a diagnosis of every vehicle.
Read the related owner discussion