Hi everyone, I own a 2005 Class C Ford E450 V10 motorhome. I am having an issue with the engine light coming on. The code is po191 which indicates the Fuel pressure sensor. I replaced this sensor and reset the code. The refueled the RV and drove a short distance before the engine light came on again. There has been times that nothing happen until i filled up the second time. I have had the fuel pressure check and was told that I am good. Not sure what to do next. Any suggestions.

 

Check the wiring/connectors for the sensor back to the PCM. Beyond that, you need to check fuel pressure under various conditions, not just idle.

The computer is seeing a fuel pressure reading that doesn't match what it expects. So if it's telling the fuel pump to pump more fuel and it's not seeing an increase in pressure (say, under a load), it'll throw this code.

Ford's service manual has diagnostic procedures to check this. Either you or someone else needs to go through that and see if there's anything wrong, before throwing more parts at it.

It could be something as simple as the fuel filter is old and clogged. Or you could need a new fuel pump. But again, don't throw parts at it.

Get an OBD-II reader (bluetooth) and use your cell phone to read the fuel pressure under various driving conditions. Report back

 

Thank you for responding. I will follow your suggestions. Will let you know what happens. Thank you

 

I have the same issue.

E450 Super duty V10 2004. The code P0191 do not want to go.

The check engine is not lighted and the motor is running really well. But still the code remain.

I changed the fuel rail pressure sensor (3 times) the last one i installed, I bought from Ford and ...it was not cheap.
I replaced the fuel filter.
I replaced the fuel pump control module.
I checked the vaccuum.
I cleaned the connector of the sensor.
I checked the pressure of fuel just befaire the filter and it is 40psi when motor is idle.
I checked the pressure with key ON but motor not running 20psi.
I unpluged the battery 25 minutes and the code was erased BUT it came back about 2 minutes after starting the motor.

And after each replacement, I erased the code BUT he always come back.

The last thing to do is to replace the pump itself and since the price of the fuel was going up ! i filled up the tank with the 55us. gallons. !!!!

2 questions:
- is there risk to use my rv for a logn raod trip ?
- any ideas on how to cerrect the situation ?

 

Your reported fuel pressures are abnormally low although, as presented, they are a bit confusing.

A P0191 is set when the FRP-measured pressure is less than the commanded pressure by a certain threshold. If I'm reading the OBDII manual correctly, it seems that the error value is 40 psi (under commanded pressure).

Per the PCED, KOEO pressure should be about 50 psi and, at hot idle, around 60 psi. These are scan tool readings via the FRP sensor. A mechanical gauge will read at least 5 psi lower.

Use your scan tool to check the FRP PID relative to your mechanical gauge at the two specified conditions. If they correlate correctly but are abnormally low, there's nothing wrong with the sensor, the problem is a lack of fuel delivery at the correct pressure. A failing fuel pump would be high on the list of suspects but there is additional diagnostic work that should be done to avoid throwing more money indiscriminately at the vehicle in the hope you guess right.

 

One thing is not clear in my head, why the engine is running well ?

Thank you, I will make these checks and keep you informed.

 

Good question. However, with only ambiguous data, it's not possible to offer a definitive opinion. Could have a fuel supply delivery issue, could have a measurement issue. Let's get unambiguous data and that should clarify things.

 

I did install a gauge before the fuel filter and now I am waiting for my mechanic to provide more info with is SnapOn 'computer' and to compare the data.

Did i mention that the 'check engine' is NOT lighted ?

Someone told me that even if the code P019 is active, if the 'check engine' is not lighted this is not an important code error and I could do my road trip (10000km) without problem !

 

Not surprised at all. Most likely you have an OBD1 calibration and the DTC is a non-MIL code.

It's not an issue until such a time is it might become one.

 

And this is why I will replace the pump. My mechanic is coming home with his scanner on wednesday so I will have more data.

In the meanwhile, I am preparing the fuel pump to go out, and 5 of the nuts were cooperative BUT the 6th one ... well a stubburn one and there is no way that the nut is coming out. BUT the bolt or hopefully the stud is turning quite easely after a nitgh soaking with liquid 'loose nut'. Yesterday it was not turning as easely as today and that let me think that it is a stud.

So I want to be sure ! they are stud aren't they ? they are NOT welded in place by the maker of the tank !

 

I did a pump replacement and beside cutting 2 bolts on the tank and having to put the tank down to make the repairs. Everything woks great.

And you were right, the problem was my pump and the P0191 like a distress signal from the pump saying ' I am exhausted '.

I had near 20psi with the key on and the motor off, now with the new pump I have close to 50psi (on my first trail). The motor run great and no more code.

Thank you everybody

 

I have an 2006 E-450 cutaway that is an RV (2006 Winnebago Aspect 26A) and I have been dealing with P0191 error codes since June 2022. Below is a write-up I did to lay out when I've had codes, actions taken, time and mileage since the codes, and to try to figure out next step.

Manufacturer – Winnebago Model - Aspect WF726A Year - 2006 Placed in Service Date - 11/03/2005 Mileage at Purchase: 30277 Purchased - 04/10/2012

In May 2023 we took a 3 week RV trip to New York, North Dakota and back. We had another problem with Check Engine and the Code: P0191 Fuel Rail Pressure Sensor Range/Performance. Below is a history of this problem, dates, corrective measures taken and results/miles until problem resurfaced.

1. June 2022 – Trip from Home to Albuquerque, NM. On the way to Albuquerque we got a Check Engine light. My brother Kristian checked the code in Albuquerque and said it was Code: P0191 Fuel Rail Pressure Sensor Range/Performance. He explained how I was to go about changing the Fuel Injection Pressure Sensor and I did this upon return home to FL. I changed the Sensor on July 11, 2022.

2. March 2023 – Trip to Silver Springs, FL. On the way there the Check Engine light came on. This was approximately 518 miles driven since I completed replacement of the Sensor, back in July (mostly short local drives near home and then about halfway to Silver Springs). After we left Silver Springs, on the way home, I went to Auto Zone and they said it was Code: P0191 Fuel Rail Pressure Sensor Range/Performance Fuel Pressure, again. So I spoke to my brother Kristian again and he recommended not to change the sensor, but instead to change the Fuel Filter and he talked me thru it and helped me over the phone to complete this replacement. This was done on March 18, 2023. From then, up until we began our recent trip in May 2023, I had driven about 141 miles, (short local drives), no Check Engine.

3. On this recent trip, May 2023, to upstate New York, then Dickinson, ND (and then home), the morning we were leaving Dickinson, on a small hill heading W, the RV downshifted and the engine revved up and we got the Check Engine light again. At this point, we had driven about 3551 miles since clearing the condition after replacing the Fuel Filter back on March 18, 2023. The RV had been driving very good and the only thing I had noticed was increased fuel economy, since replacing the Fuel Filter back in March. Since we were only 16 miles from Belfield, ND and were headed that way, I had my brother-in-law Chris check it out, (he has an automotive shop there). He said it was the same code. Also, his computer he had hooked to the RV said at idle, the system wanted 65psi from the Fuel Pump, but was getting 52psi. He ran a computer diagnostic and then reset the code and we headed on our way. We made it all the way home to FL and also took the RV on a short drive (25 miles round trip). Despite many instances of it downshifting and the engine revving up, we have not had the Check Engine light again. We have gone about 2417 miles since he reset it in Belfield, ND. And just this weekend we took a short 74 mile trip, still no error code.

So I’m not sure what to do now. My brother Kristian thinks the next best step would be to compare the pressures with a manual gauge vs. what the electronics are saying. He also thinks it is some electrical issue, maybe a wire that intermittently stops making contact. Can you please evaluate, and let me know what you think I should do.

 

I too have a class C E450 and replaced the sensor to no avail. I’ve driven it 20k miles with no issues. I’m getting ready to sell it so I’d like the next owner not to have to worry.

on RV forums I’ve read about a voltage drop between the pump and sensor but have very little info on how they tested and solved it. One site recommended changing the pump but I’m not getting into that without good reason.

thanks in advance.

 

I never read that. Since I replaced the Sensor on the Fuel Rail, and the Fuel Filter and after that one instance of getting the code, with possible water getting in the fuel in late May 2023, we have not had the code again.

 

Thank you. I’ll try that again. Maybe the first one was a dud. I’ll follow up with the results.