Rail press. regulator valve(RPR) is installed in common rail and controls common rail pressure fast as regulating returning quantity of fuel which is delivered to common rail when fast rise of rail pressure is required like the moment of turning engine ON or when fast relief of pressure is required like at the point of deceleration.
The lower RPRV current is, the more fuel is supplied to common rail. Thus it leads rail pressure to be high. On the contrary, the higher RPRV current is, the less fuel is supplied to common rail.
P0091 is set when "0"A in control circuit of Rail Pressure regulator valve(integrated with common rail) is detected for more than 0.11 sec. This code is due to open of short to ground in control circuit or Rail Pressure regulator valve internal open.
Item
Detecting Condition
Possible Cause
DTC Strategy
Voltage monitoring
RPRV circuit
RPRV component
Enable Conditions
IG KEY "ON"
Threshold Value
Short to GND, Wiring open
Diagnostic Time
220ms
Fail Safe
Fuel Cut
NO
EGR Off
Fuel Limit
YES
Check Lamp
Rail pressure regulator valve resistance
Operating frequancy
3.42 ~ 3.78? (20?)
1000Hz(1KHz)
Fig.1) Waveform of rail pressure regulator valve at idle. It shows approx. 20% duty.
Fig.2) Waveform of rail pressure regulator valve as accelerating. Approx. 50% duty is outputted as engine load increases.
( When rail pressure increases as accelerating, rail pressure regulator valve duty(current) rises.)