fuel rail pressure sensor "A" circuit performance

Tony from Balgowlah Manager Posted   Latest  
Question
Driveability
2010 Jeep Grand Cherokee Limited 3.0L (M) 5-spd (545RFE)
P0191 - Fuel Rail Pressure Sensor Circuit Range/Performance Bank 1

Not a hard fault, can take 200km till fault happens. 244209km on clock, some help to track down fault? have changed fuel filter. 

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Michael from Champaign

 

Diagnostician
 

DId you by chance save the freeze frame on the code to see when it triggered? And if so can you post it so we can take a look at it?

+1

Peter from Langley

 

Owner
 

Are these the same motors as the sprinters? I think They are and if so, have a good hard look at the pressure sensor filter and see if has debris. We had an injection pump fail and wreak havoc in the sytem. 

-1

Isaac from Hurdle Mills

 

Diagnostician
 

No this will be an eco diesel. Vm platform. 

+1

Peter from Langley

 

Owner
 

Gotcha, thanks.

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Tony from Balgowlah

 

Manager
 

Hi Michael, we do have a freeze frame but having trouble attaching it. Do you know what format it should be in ??

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Scott from Claremont

 

Manager
 

Hi Tony,

A graphic file is what we currently support. JPEG or PNG file will work fine.

Let me know if you have any trouble.

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Michael from Champaign

 

Diagnostician
 

Great, get it up and let's see if we can figure it out.🙂

+1

Tony from Balgowlah

 

Manager
 

Hi Michael, lets see how we went this time !

cheers

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Tony from Balgowlah

 

Manager
 

hi

Hi Michael, did you get the Freeze frame data and any thoughts?

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Michael from Champaign

 

Diagnostician
 

The code triggered with the engine not running. See if in the service info if it gives you a pressure to voltage chart for the sensor and see if it matches for the pressure. If it doesn't check power, ground, signal to the sensor with a scope or dvom and then make sure the signal voltage at the sensor matches with what the computer sees. Do this and let me know what you find.

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Chris from Commack

 

Diagnostician
 

I agree, lets not get too crazy. Lets start with the basics. Your actual and specified fuel pressure don't match. Do they match while the engine is running? Your code could be caused by low fuel pressure, but it could also be caused by a sensor power/ground issue. 

Let's start by getting a running capture. idle and under load. lets make sure this low pressure pump can keep up. 

Second, lets check the powers and grounds to the sensor. I don't think we have enough to go on yet to make a solid diagnostic call.

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Michael from Champaign

 

Diagnostician
 

Tony did you get the issue resolved?

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Tony from Balgowlah

 

Manager
 

Still on going, will keep you posted. 

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Tony from Balgowlah

 

Manager
 

Hi Michael, thanks for getting back to me, Unfortunately we haven't resolved it. The owner has decided to go and trade the car in as he doesn't want to spend any more money on it [which is understandable]. He appreciated all the effort but it was at the stage where it didn't matter what path we took it was going to cost a lot to sort out. Thanks again for all your help, we've enjoyed "talking" on the diagnostic network

cheers

Tony

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Brian from Willoughby

 

Diagnostician
 

The code did set at KOEO. However, do you have scan data with it running? It appears the actual pressure is lower than desired from the freeze frame data you submitted. Are there any driveability complaints? Poor performance etc? If not, there could be a chance that the sensor could be inaccurately reporting lower pressure than what's truly in the rail. Circuit tests need to be performed as previously explained as well. High resistance in a sensor circuit can skew it's voltage back to the ecu. 

+1

Michael from Holt

 

Diagnostician
 

I think the first step would be to verify circuit integrity on this test your reference voltage your ground and signal wire and make sure you dont have spread terminals. Once you know your circuit is intact hook up a scope if ones available to the signal circuit and ensure while driving its not dropping out. Is there a lack of power or running issues at all or just the check engine light with code. I would be leaning torwards a circuit issue as freeze frame indicates set while off.

+1

Brin from Melbourne

 

Diagnostician
 

Hey Tony,

I would recommend sharing a little more information with us. We can see from the freeze frame data that the code set with the engine off but we don't know if that has always been the case. Do you know if the code set under different conditions? I would of course perform a visual inspection first but my next step would be to set up a scan tool to record your data while test driving this vehicle to monitor the fuel rail pressure actual and compare with desired. 

I can see that this is most likely a OM642 Mercedes Engine but I can't get any meaningful service information on it. 

Find useful service information to get a more thorough understanding of code set criteria, figure out how to duplicate the concern and test under those conditions. 

It looks like actual fuel rail pressure is not matching desired during the fault. You either have an actual intermittent fuel rail pressure concern or an intermittent erratic sensor circuit concern. I would also manipulate the fuel rail pressure sensor, connector and harness while monitoring the signal with a scan tool. If you see a concern, verify it with a scope. 

+2

Isaac from Hurdle Mills

 

Diagnostician
 

This is an eco diesel vm platform not the Mercedes unit. 

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Brin from Melbourne

 

Diagnostician
 

It looks like this is a Global Code. If so, can you check for enhanced fault codes. Build the vehicle in the scan tool instead of going into the Global OBD/Generic side of the scan tool. 

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Chuck from Sylvania

 

Diagnostician
 

Ran into that once on an Isuzu NPR, found a break in the wiring about 3 inches from the sensor inside the harness.

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