DTC Advanced Diagnostics: P0191 (3.0L Engine)
DTC P0191: Fuel Rail Pressure Sensor Circuit Range/Performance Problem
General Description
The fuel rail pressure sensor senses fuel pressure and converts it into electrical signals. The powertrain control module (PCM) monitors the fuel pressure of which certain duration has passed from the vehicle OFF (LOCK) mode, and it is used for the malfunction determination. If the fuel pressure of which certain duration has passed from the vehicle OFF (LOCK) mode is not lowered from the fuel pressure of the previous vehicle OFF (LOCK) mode, or if the fuel pressure after the engine start does not increase from the fuel pressure of which certain duration passed from the vehicle OFF (LOCK) mode, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | - |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
Stuck high
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after the vehicle is turned to the OFF (LOCK) mode | 6 hours | - |
| Engine coolant temperature lowering amount during vehicle OFF (LOCK) mode | 55.7 deg.F (30.9 deg.C) | - |
| Engine coolant temperature right before the vehicle is turned to the OFF (LOCK) mode of previous run | 140 deg.F (60 deg.C) | - |
| Intake air temperature [IAT sensor (1)] | - | 122 deg.F (50 deg.C) |
| Maximum fuel pressure during the previous run | 14.5 MPa (147.857 kgf/cm 2, 2, 103.08 psi) | - |
[ ]: HDS Parameter
Stuck low
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after the vehicle is turned to the OFF (LOCK) mode | 6 hours | - |
| Fuel level | 15 % | - |
| High pressure fuel pump command | Maximum | |
Malfunction Threshold
- Stuck high
Fuel pressure right before the vehicle is turned to the OFF (LOCK) mode of previous run - (minus) fuel pressure right after the vehicle is turned to the ON mode of which more than 6 hours have passed from the previous vehicle OFF (LOCK) mode is less than 0.1 kPa (0.001 kgf/cm 2, 0.01 psi) for at least 300 milliseconds.
- Stuck low
Fuel pressure of which more than 6 hours has passed from the vehicle OFF (LOCK) - (minus) fuel pressure after the engine start is less than 1.0 kPa (0.01 kgf/cm 2, 0.15 psi) for at least 300 milliseconds.
Possible Cause
- Low fuel pressure pipe failure (clogged, deformed, coming off)
- High pressure fuel pump failure (low delivery)
- High fuel pressure pipe failure (clogged, deformed, coming off)
- Injector failure (keeps injecting)
- Fuel rail pressure sensor failure
Confirmation Procedure
Operating Condition
- Refuel if the fuel level is 15 % or less.
- Start the engine. Hold the engine speed [Engine Speed] at 3, 000 rpm without load (in P or N) until the radiator fan comes on.
- Drive the vehicle with wide open throttle for 5 seconds or more.
- Turn the vehicle to the OFF (LOCK) mode and leave it for 6 hours or more.
- Start the engine.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.