Fuel System Pressure Control
Fuel Rail Pressure Monitors
The pressure in the fuel rail is controlled by a closed-loop control strategy that is always active during vehicle operation. Two controllers may be used to control the rail pressure: the Pressure Control Valve and the Volume Control Valve. The Pressure Control Valve is used to control pressure at engine start and when fuel temperature is low. The Volume Control Valve is used to control fuel pressure under most other conditions. A third operation mode allows fuel rail pressure to be controlled by a combination of the Pressure Control Valve and Volume Control Valve; this mode is typically used to transition from control by one device to the other and in regimes where low fuel volume is required.
The fuel rail pressure is controlled either with the Pressure Control Valve, the Volume Control Valve, or both, depending upon engine operation condition. The high and low Fuel Rail Pressure Monitors detect when there is an excessive deviation from the desired fuel pressure when the controller has reached a control limit or when the minimum or maximum allowable rail pressures are exceeded.
| DTCs | P0087 - Fuel Rail/System Pressure - Too Low P0088 - Fuel Rail/System Pressure - Too High P0093 - Fuel System Leak Detected - Large Leak |
| Monitor Execution | Continuous |
| Monitor Sequence | None |
| Sensors OK | FRP (P0191, P0192, P0193) |
| Typical Monitoring Duration | P0087, P0088 - 1.4 sec P0093 - 2 sec |
| P0087:
If the commanded rail pressure exceeds the measured rail pressure by 250 bar for 1.4 sec or if the measured rail pressure drops below 140 bar for 0.3 sec P0088: If the measured rail pressure exceeds the commanded rail pressure by 250 bar for 1.4 sec or if the measured rail pressure exceeds 2150 bar for 0.3 sec P0093: If the set point needed for the volume control valve to maintain desired rail pressure exceeds 13, 500 mm3/sec at idle or if the set point needed for the volume control valve to maintain desired rail pressure is 40% greater than the volume control valve set point as calculated from the requested injection quantity when not at idle |