P0087 p0088 the jeep is going in to limp mode,there is new lift pump fited , new fuel filter, two injectors was leaking i got them rebuild, i had change fuel presure regulator and still sometimes she is ging to limp mode.fuel presure is 5000kpa at 750rpm, 20000kpa at 3500rpm.why she is showing two codes p0087 fuel pressure to low, and p0088 fuel presurre to high.make no sens to me .

Hi there! I have the same Issue. Did you find the problem by any chance?

I would check for an air leak in the fuel pipe.

code p 0171 refers to system too lean bank 1== causes --intake /exhaust leak---AIR system---MAF/VAF sensor ---fuel pressure/pump--- injectors--- Heated oxygen sensor
by changing the O sensor (oxygen sensor ) you changed the wrong one and so there would be no change to the read out there
code p 2173 refers to throttle actuator control (TAC) system -high air flow detected ===causes --intake system---throttle body
fix the causes and you stand a chance of fixing the problem

PO251 is Injection pump metering control problem according to my list of codes
Get a leak down test done on the injectors to see if they are ok as generally they are the reason . Also pull the fuel filter and drain it into a clean container and check for swarf in the fuel. The replacement parts. The glow plug light coming on is a related issue.

DTC P0087: Fuel Rail Pressure (FRP) Too Low

Circuit/System Description
The fuel injection pump supplies high pressure fuel to the fuel injection rails, and then to the fuel injectors through high pressure pipes. The fuel rail pressure (FRP) sensor is a three wire sensor mounted in the right fuel injection rail. The FRP sensor uses a 5-volt reference circuit , a signal circuit, and a low reference circuit to monitor fuel rail pressure. This information is sent to the engine control module (ECM) to assist in the fueling of the engine.

Fuel Pressure Regulator Solenoid Supply Voltage
P0088, P0090
P0088
P0090
P0087, P0191, P2510
Conditions for Setting the DTC
P0087
• The actual FRP is more than 15 MPa (2,176 psi) below the desired FRP.
OR
• The actual FRP is less than 22.5 MPa (3,263 psi).

Action Taken When the DTC Sets
• DTCs P0087 and P0088 are Type A DTCs.
• The ECM commands the engine to operate in the Reduced Engine Power mode.
• The message center displays Reduced Engine Power.

Important: Because of the cleansing properties of the biodiesel, switching from the straight diesel to a biodiesel blend can prematurely restrict the fuel filter with normal deposits in the fuel system. A fuel filter replacement might be required sooner than the recommended interval.
P0087
If DTC P0090, P0168 or P0191 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
Ignition ON for 90 seconds, verify the scan tool FRP Regulator Command parameter is less than 20 percent.
? If greater than the specified range, replace the ECM.
Attempt to start the engine.
? If the engine does not start, refer to Engine Cranks But Does Not Run.
Install the CH-48027 to the fuel rail service port and slowly increase the engine speed until reaching wide open throttle (WOT). The value should be between 1-4 inches Hg vacuum.
? If more than the specified value, inspect for restricted fuel filter or damaged supply lines.
? If no restriction was found, test for high fuel return flow. Refer to Fuel System Diagnosis - High Pressure Side.
With the engine idling or at an idle, command the fuel pressure control to 180 MPa (26,106 psi) with a scan tool. Observe the Actual Fuel Rail Pressure parameter. The actual fuel pressure should be the same as the commanded pressure.
? If the Actual Fuel Rail Pressure is less than 165 MPa (23,931 psi), refer to Fuel System Diagnosis - High Pressure Side.
Important: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint, or in the Failure Records for this DTC, inspect for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On.
Operate the vehicle within the conditions for which the customer complaint occurs while observing the CH-48027 . You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records.
? If the vacuum was more than 12 inches Hg of vacuum at any time in the operating range, inspect for kinked or restricted fuel supply lines.
Operate the vehicle within the conditions for which the customer complaint occurred. Observe the Actual fuel Rail Pressure and Desired Fuel rail Pressure parameters with a scan tool. Fuel pressures should be the same for both parameters.
? If the Actual Fuel Rail Pressure is less than the Desired Fuel Rail Pressure, refer to Fuel System Diagnosis - High Pressure Side.
? If fuel system tests normal, refer to Diagnostic Aids.

P0087 GMC - Fuel Rail Pressure Malfunction Pressure Too Low

Possible causes - Faulty fuel pump
- Blocked fuel filter
- Faulty fuel pressure sensor
- Fuel pressure sensor harness is open or shorted
- Fuel pressure sensor electrical circuit poor connection
- Faulty Fuel injector

4 possible answers 1, pollon filter 2,exlorator peddle, 3 fuel module
4,fuel pressure rail , have you had it pluged in for faults

P0087 is a low fuel rail pressure code. One of 2 likely causes. the quick diagnosis is to turn the key into the "on" position and listen for the fuel pump hum. If there is a hum, but the van doesn't start, I would then check the fuel filter. in between 80k and 100k miles, some of the sprinters run into a fuel filter issue where the fuel is too restricted to flow to the injectors properly. If you don't get enough fuel through the injectors, the engine will rotate, but not get enough vapor concentration to start.

P0087- low pressure fuel system. Fuel pressur valve stock open, Fuel volume control valve stuck close, Leaking fuel injector,P0088- fuel pressure contorl valve stuck close, Fuel rail pressure sensor P2291-all @ at the above, means to say poor fuel quality

45 PSI