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[Engine] Fuel Rail Pressure Sensor Voltage Faulty
#1
My Story, Berlingo 2008 Hdi

The car was occasionally cutting out with error P0192, Fuel rail pressure sensor circuit low input, I’d reset the error, then it would run ok for a few days, episodes getting more frequent.

A year earlier I had the EGR had come loose and the exhaust gases had melted the air filter box, so I suspected heat damage. I removed the plug from the fuel rail pressure sensor, and it was badly melted. I got a replacement with cable from a breaker and spliced it in and replaced the sensor.

Since then, the car refuses to start, returning P0193 at all times, Fuel rail pressure sensor circuit high input. 

Checking the voltages on the fuel rail pressure sensor pins, I get pin 1, 12.2v, pin 2, 0v, pin 3, 2.7 volts with the sensor connected, and 10 volts with the sensor disconnected. This is the same with a different new sensor.

This is not what I expected as all the information I have makes me think I should have 5v on pin 1, (as most sensors have a 5v reference line), and the sensor returning 0.5 volts on pin 3 corresponding to air pressure.

If I remove the sensor and connect pin 3 to pin 2 through a 1000ohm resistor, the voltage on pin 3 goes to near zero volts, but still reads error P0193. In a similar way, using two resistors and achieving 6 volts on pin 3 still shows error P0193. (I am resetting the codes between and during tests)

To be able to go any further and find the source of the 12v I need a wiring diagram. This voltage probably comes from the ECU, but it could come from a relay. 

Does anyone have a wiring diagram or can offer any suggestions please.?
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#2
does,nt the 5v type refer to an analogue sensor, and yours a pwm/duty cycle type ?
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#3
This any use to you ?  the poster is no duffer by the way !!!

https://www.berlingoforum.com/thread-10221.html

I have to say it does sound like your wiring is awry by having the 12.2V
[-] The following 1 user says Thank You to geoff for this post:
  • kevinadam
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#4
I'm not 100% sure if this is the correct diagram for your engine, but is looks fairly generic so will hopefully be of some use. This comes from Sedre which is fairly easy to find online but a pain to install & a bit of a faff to use.


Attached Files
.pdf   B9 Fuel Inj.pdf (Size: 382.07 KB / Downloads: 7)
[-] The following 2 users say Thank You to cancunia for this post:
  • frank, kevinadam
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#5
From the pic it seems as ordinary 3 wire sensor. You can use
link Geoff sent you for testing it. But, you will need to create 100-150 bar pressure
to test that sensor. Really don't know how to accomplish that.
That sensor is after HP pump and measures how much pressure pump is creating.
If there is any problem in that ECU will refuse to operate injectors.
You can't fool ECU by resistor, because that is really good safety measure

I have seen sensors input 12v and output 0-5v . I don't know if that sensor is like that.
90% sensors input 5v and output 0-5v.

Here is good info on testing with oscillosope:
https://www.picoauto.com/library/automot...il-diesel/

Also you can have problem in pump itself. Pump can't produce required pressure
or it is producing too much pressure.

Best regards,
brajomobil
[-] The following 2 users say Thank You to brajomobil for this post:
  • frank, kevinadam
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#6
Thanks for all of the replies. I found the problem, after collecting the wiring diagrams. I got the 'easymanuals' version of the workshop service manual, for about £14. A huge download of 18GB and a bit complex to install, but it is a great resource and has comprehensive wiring diagrams.

Then I removed the ECU and meter checked the wires from the plug I had replaced. Basically the wires on the plug I had replaced didn't go to the correct part of the ECU. It suggested that the lug should be attached to the 'water in fuel' sensor, which I don't have. Then the penny dropped! There are two identical three pin plugs about 3 inches from each other, hidden down the back of the engine block, and I had replaced and connected the wrong one back on to the fuel rail pressure sensor. Doh!

The original fault turned out to be a failing fuel rail pressure sensor. You live and learn, painfully.
[-] The following 1 user says Thank You to kevinadam for this post:
  • frank
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#7
(07-11-2018, 10:11 AM)cancunia Wrote:  I'm not 100% sure if this is the correct diagram for your engine, but is looks fairly generic so will hopefully be of some use. This comes from Sedre which is fairly easy to find online but a pain to install & a bit of a faff to use.

It is close enough! Thanks very much.
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#8
(07-11-2018, 12:15 AM)geoff Wrote:  This any use to you ?  the poster is no duffer by the way !!!

https://www.berlingoforum.com/thread-10221.html

I have to say it does sound like your wiring is awry by having the 12.2V

Yes, a brilliant explanation. By the time I was finished I had one broken, one second hand one and one new one to practice on.
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#9
Glad you had a result !
[-] The following 1 user says Thank You to geoff for this post:
  • kevinadam
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