P0088 code

[K5IP]

I originally posted under 911 but now am home.
The P0088 code for high rail pressure haunted me for the last 1300 miles.
Now that I am home I connected my scanner and the following codes were present:
P0088 fuel rail too high.
P0234 turbo over boost condition.
P0251 injection pump fuel metering control.
I understand that I have a problem with either the FCA or the Rail pressure sensor, but can the obd2 scanner differentiate between the FCA and rail sensor, (as it seems to imply).
Also, this is an intermittent problem. I erased the codes and none have come back in the lase few hundred miles. So, which is the more probable failure (i.e. can the FCA stick)
Should I just replace them both?
Thanks for all the help with the 911 replies (Cerb).
Rog

 

[p-Bar]

If the FCA was bad you would have rough running conditions . I would tend to look at the rail sensor. I notice you have a ham radio could that be the culprit?
Just saw this thread : https://www.turbodieselregister.com/threads/248136-03-hi-fuel-rail-psi-at-idle

I know its at idle but....

 

[K5IP]

P-Bar,
Radio was not on at the time. The truck was running smooth but MPG was bad, possibly due to high winds. Normal MPG with my small trailer is about 15 MPG. Only got about 11 on this trip.
I would think if the rail pressure was actually high I would have noticed more power but I did not. So, if I did not perhaps the pressure sensor was outputting a high condition causing the FCA to pull back the rail pressure.. In a closed loop configuration it is really hard to troubleshoot unless you have some external monitor. Still thinking.
Rog

 

[p-Bar]

yes understand and as you know intermittent problems are the worst to diagnose . guess keep driving

 

[p-Bar]

try changing the fuel filter

 

[cerberusiam]

All that is missing is a 2509 and I would say you have a connection issue somewhere. Ground point, battery cables, batteries, etc. That is easy to check and and fix if it is so.

It is also possible the FCA is sticking letting in more fuel than is demanded causing the high rail pressure signal and over speeding the turbo with the extra fuel before the ECU can compensate.

Couple of things to check and think about.

 

[K5IP]

Cerb,
I think you nailed it.
I was not worried or even thinking about the over boost code but you are right in thinking that could have been due to the rail pressure actually being high.
That being the case I guess I will change the FCA first. It the least expensive of the two parts anyhow.
By the way, does the FCA actually reside in, and modify the fuel flow, or does it simply operate something in the pump to regulate pressure?
Thanks
Rog

 

[cerberusiam]

Yes, the FCA is in the fuel flow and regulates how much is supplied to the rail. It is a solenoid that uses a PWM signal to move a check valve the allows fuel into the high pressure side of the pump. Rememebr the old way of telling if they are good by shaking them, if they rattle they are good? The rattle is the check valve, a funky 3 sided piece. If it gets sticky and starts hanging the ECU cannot meter the fuel correctly because it doesn't react as designed. The differences can be subtle but the results are bad idle and dying, rail pressure bouncing all over the place high or low, problems draining the rail under high load, etc. The modded FCA's are really picky. They can look perfectly fine but still throw glitches into things. Sometimes all you can do is change them and see if it solves the problem.

Usually a new one from Bosch, or even a new modified one, is pretty solid as to its function. Heaven help us if that piece ever gets outsourced to the cheapest vendor or they start trying to reman them. No end to problems in that scenario.

 

[Perrymedic]

Just changed my fuel filter and now getting this code. Any thoughts?

 

[p-Bar]

Just changed my fuel filter and now getting this code. Any thoughts?

Can you reset it ?

 

[Perrymedic]

Would that entail disconnecting the batteries? Truck runs great. I am thinking of powering down and unplugging the sensor and then replugging it in.

 

[p-Bar]

No going to auto parts stroe and have them reset it. OBDII port

 

[HerbW]

No going to auto parts stroe and have them reset it. OBDII port

K5IP, I bought an OBDII tool from Harbor Freight and you plug it into the OBDII port under the steering wheel. Then read and clear codes at will. I have an Edge Evolution and it also has P codes readings and the clearing of codes quickly. I think other things like Edge also has trouble code reader and clearing ability. Good luck, Herb